Probe and Ponder
Q1. Can we make mirrors which can give enlarged or diminished images?
Answer:
Yes, spherical mirrors (concave and convex) can produce enlarged or diminished images. A concave mirror can produce enlarged images when the object is placed close to it. A convex mirror always produces diminished images.
Q2. On side-view mirrors of vehicles, there is a warning that says "Objects in mirror are closer than they appear". Why is this warning written there?
Answer:
Side-view mirrors are convex mirrors. They produce diminished images, which makes objects appear smaller and farther away than they actually are. The warning is to alert drivers that the actual distance is less than what is perceived through the mirror, helping them judge distances correctly while driving.
Q3. Why is there a curved line on some reading glasses?
Answer:
Reading glasses use convex lenses to correct presbyopia (age-related farsightedness). The curved shape of the lens bends light rays to focus them correctly on the retina, helping people see nearby objects clearly.
Activity 10.1
Q1. Take a shiny metallic spoon and hold its curved surface close to your face. Can you see your image in it? Notice the image of your face. Is it different from the image you see in a plane mirror? While observing the image, slowly move the spoon away from your face. Do you observe any change in the image? Now flip the spoon and repeat the same steps. Did you notice that the shiny metallic spoon acted like a mirror and you could see your image in it? When you looked at the inner side of the spoon which is curved inwards, you must have observed that the image was inverted (Fig. 10.1a). When you looked at the outer side of the spoon which bulges outwards, the image of your face was erect but smaller in size (Fig. 10.1b). 
Answer:
The inner curved surface of the spoon acts like a concave mirror, forming an inverted image when the face is close. The outer curved surface acts like a convex mirror, forming an erect but diminished image. As the spoon is moved away, the image changes in size and orientation.
Activity 10.3
Q1. Take a concave mirror, a convex mirror, two small wooden blocks or something similar to place the mirrors in an upright position, and a small toy or some other object. Place the two mirrors side by side in an upright position on a table. Keep the object in front of them at a small distance (3-4 cm away) as shown in Fig. 10.5a. What kind of images do you see in each mirror? Are the images of the same size as the object? Are they erect? Do you see lateral inversion in the images? Write down your observations in your notebook. Now slowly move the object away from the mirrors (Fig. 10.5b). What changes do you see in the images in both the mirrors? Do the images become smaller or larger? Do they continue to be erect? Again, note down your observations. Repeat the steps with each mirror individually. Analyse your observations and draw conclusions. 
Answer:
Concave mirror: When the object is close, the image is erect and enlarged. When moved away, the image becomes inverted; initially enlarged, then it gets smaller.
Convex mirror: The image is always erect and diminished in size, regardless of the object's distance. The size of the image decreases slightly as the object is moved away.
Activity 10.4
Q1. Collect a plane mirror with stand, a torch, a comb, a paper clip to hold the comb upright, a sheet of white paper, and a strip of black paper. As you did earlier, make a thin slit by covering all openings of the comb using black paper, except for one in the middle. Spread a sheet of white paper on a table. Place the plane mirror upright on it. Using the thin slit and torch, obtain a thin beam of light along the paper and adjust it to fall upon the mirror as shown in Fig. 10.8a. Now, move the slit and torch slightly so that the beam of light falls at a different angle on the mirror (Fig. 10.8b). Does the reflected beam of light also shift? Make the beam of light fall on the mirror at different angles and observe how the direction of the reflected beam changes. 
Answer:
This activity demonstrates the law of reflection. As the angle of incidence changes, the angle of reflection also changes accordingly. The reflected beam shifts when the incident beam is moved, and the angles are always equal.
Activity 10.5
Q1. Use the same setup as in Activity 10.4, but place a stiff sheet of chart paper flat on a table such that part of it extends beyond the edge of the table. Shine a beam of light on the mirror placed on the sheet and observe the reflected beam on the extended portion (Fig. 10.10a). Now, bend the extended part of the sheet along the edge of the table (Fig. 10.10b). Do you still see the reflected beam on the extended portion? Flatten the paper again and observe. The reflected beam disappears when the sheet is bent but reappears when it is flattened again. This shows that the reflected beam lies in the same plane as that of the incident beam. Bending the sheet creates a new plane, breaking this alignment. 
Answer:
This activity demonstrates the second law of reflection: the incident ray, the normal, and the reflected ray all lie in the same plane. When the paper is bent, the reflected ray is no longer on the same plane as the incident ray, so it is not visible on the paper.
Activity 10.6
Q1. Collect a plane mirror, a concave mirror, a convex mirror, stand for mirrors, a torch, a comb, and a paper clip to hold the comb upright. Use the same setup as Activity 10.4 again, but instead of a single slit, leave many openings of the comb uncovered to obtain multiple parallel beams of light (Fig. 10.11a). Let the multiple parallel beams of light fall upon the plane mirror, concave mirror, and convex mirror, one by one. Observe the reflected beams. Is your observation similar to what is shown in Fig. 10.11 (b), (c), and (d)? When multiple parallel beams of light fall upon a plane mirror, the multiple reflected beams are also parallel (Fig. 10.11b). However, when multiple beams of light fall upon a concave mirror, the multiple reflected beams get closer, that is, they converge (Fig. 10.11c). Whereas, in the case of a convex mirror, the multiple reflected beams spread, that is, they diverge (Fig. 10.11d). 
Answer:
This activity shows that a plane mirror reflects parallel beams as parallel beams. A concave mirror converges the reflected beams (focuses them). A convex mirror diverges the reflected beams (spreads them out).
Activity 10.7
Q1. Take a concave mirror and a sheet of thin paper or newspaper. Hold the concave mirror with its reflecting surface facing the Sun. Direct the light of the Sun reflected by the mirror on the sheet of paper. Adjust the distance of the paper until you get a sharp bright spot on it as shown in Fig. 10.12. Hold the mirror and the sheet of paper steady for a few minutes. Does the paper start to burn producing smoke? The bright spot is formed on the paper because light from the Sun, after reflection from the mirror, gets concentrated on this point. This produces sufficient heat at this point which can ignite the paper. 
Answer:
Concave mirrors converge sunlight to a point (focus), concentrating the energy. This can generate enough heat to burn paper. This shows the focusing property of concave mirrors.
Activity 10.8
Q1. Collect a flat strip of glass or clear plastic, such as a flat scale, few drops of oil, dropper, water, and a paper or book with some text printed on it. Spread a few drops of oil on the surface of glass or plastic strip and rub it to leave a very thin coating. You can also use wax instead of oil. Using a dropper or your finger, place a small drop of water on the oiled/waxed spot. (The oil/wax helps the water form a nice round drop.) Examine the water drop. What is the shape of its surface? Is it flat or curved inward or curved outward? Place the paper underneath the glass/plastic strip such that the text is directly under the water drop (see Fig. 10.13). Now, look down through the water drop at the text below. Do you find some change in the size of the letters just below the water drop? Do they look enlarged or smaller? 
Answer:
The water drop has a curved (convex) surface and acts like a convex lens. It magnifies the text underneath, making the letters appear larger. This demonstrates how a convex lens works.
Activity 10.9
Q1. Collect a convex lens, a concave lens, a lens holder, and a small object. Take the convex lens and place it upright using its holder. Place the object behind the convex lens (it may also be placed on something to bring it up to the level of the lens). Look at the object through the lens from the other side of the lens (Fig. 10.17a) and note your observations in your notebook. Now slowly move the object farther from the lens and keep observing how the image changes (Fig. 10.17b). How does the distance of the object from the convex lens affect how it looks? Now repeat the steps using a concave lens (Fig. 10.17c). Analyse your observations recorded in your notebook and compare the images seen through both lenses. What conclusions do you draw? 
Answer:
Convex lens: When the object is close, the image is erect and enlarged. As the object is moved away, the image becomes inverted; initially enlarged, then it gets smaller.
Concave lens: The image is always erect and diminished in size, regardless of the object's distance.
Activity 10.10
Q1. Collect a thin transparent glass plate, a convex lens, a concave lens, a torch and a comb to obtain multiple parallel beams of light, a paper clip to hold the comb upright, two identical books, and sheets of white paper. Using two books placed adjacent to each other, fix the glass plate or lens upright in between them as shown in Fig. 10.18. Spread paper sheets on both books. Now let the multiple parallel beams of light fall upon the thin glass plate, convex lens, and concave lens one by one as shown in Fig. 10.18. Does the parallel beam of light pass through as it is in all three cases? Record and analyse your observations. The light beam passes through the thin glass plate as it is. The convex lens converges the light falling on it while the concave lens diverges the light. A convex lens is also called a converging lens while a concave lens is called a diverging lens. 
Answer:
Light passes straight through a flat glass plate without changing direction. A convex lens converges parallel beams to a point (focus). A concave lens diverges the beams, spreading them out.
Activity 10.11
Q1. Repeat Activity 10.7 by putting a convex lens in the path of sunrays in place of a concave mirror (Fig. 10.19). Could you burn the paper? 
Answer:
Yes, a convex lens can also converge sunlight to a point and burn paper, just like a concave mirror. This shows that convex lenses can focus light and concentrate heat.
Questions and Activities
Q1. A light ray is incident on a mirror and gets reflected by it (Fig. 10.21). The angle made by the incident ray with the normal to the mirror is 40°. What is the angle made by the reflected ray with the mirror? (i) 40° (ii) 50° (iii) 45° (iv) 60° 
Answer:
Answer: (ii) 50°
The angle of incidence is 40°, so the angle of reflection is also 40°. The angle between the reflected ray and the mirror is 90° - 40° = 50°.
Q2. Fig. 10.22 shows three different situations where a light ray falls on a mirror: (i) The light ray falls along the normal. (ii) The mirror is tilted, but the light ray still falls along the normal to the tilted surface. (iii) The mirror is tilted, and the light ray falls at an angle of 20° from the normal. Draw the reflected ray in each case (Use a ruler and protractor for accurate drawing). What is the angle of reflection in each case? 
Answer:
(i) When the light ray falls along the normal, the angle of incidence is 0°, so the angle of reflection is also 0°. The ray reflects back along the same path.
(ii) Even when the mirror is tilted, if the ray falls along the normal to the tilted surface, the angle of incidence is 0°, so the angle of reflection is 0°.
(iii) If the angle of incidence is 20°, the angle of reflection is also 20°.
Q3. In Fig. 10.23, the cap of a sketch pen is placed in front of three types of mirrors. Match each image with the correct mirror.
| Image | Mirror |
|---|---|
| (i) | Plane mirror |
| (ii) | Convex mirror |
| (iii) | Concave mirror |
Answer:
Image (i) is of the same size and erect → Plane mirror.
Image (ii) is diminished and erect → Convex mirror.
Image (iii) is enlarged and erect → Concave mirror (object close to the mirror).
Q4. In Fig. 10.24, the cap of a sketch pen is placed behind a convex lens, a concave lens, and a flat transparent glass piece — all at the same distance. Match each image with the correct type of lens or glass.
| Image | Lens/glass type |
|---|---|
| (i) | Flat transparent glass piece |
| (ii) | Convex lens |
| (iii) | Concave lens |
Answer:
Image (i) is of the same size → Flat transparent glass piece.
Image (ii) is enlarged → Convex lens.
Image (iii) is diminished → Concave lens.
Q5. When the light is incident along the normal on the mirror, which of the following statements is true: (i) Angle of incidence is 90° (ii) Angle of incidence is 0° (iii) Angle of reflection is 90° (iv) No reflection of light takes place in this case
Answer:
Answer: (ii) Angle of incidence is 0°
When light is incident along the normal, it falls perpendicular to the surface, so the angle of incidence is 0°. The reflected ray also goes back along the normal, so the angle of reflection is also 0°.
Q6. Three mirrors—plane, concave and convex are placed in Fig. 10.25. On the basis of the images of the graph sheet formed in the mirrors, identify the mirrors and write their names above the mirrors. 
Answer:
Mirror A: Concave mirror (image is inverted and enlarged).
Mirror B: Plane mirror (image is same size and erect).
Mirror C: Convex mirror (image is diminished and erect).
Q7. In a museum, a woman walks towards a large concave mirror (Fig. 10.26). She will see that: (i) her erect image keeps decreasing in size. (ii) her inverted image keeps decreasing in size. (iii) her inverted image keeps increasing in size and eventually it becomes erect and magnified. (iv) her erect image keeps increasing in size. 
Answer:
Answer: (iii) her inverted image keeps increasing in size and eventually it becomes erect and magnified.
As she walks towards a concave mirror, she first sees an inverted image that grows larger. When she is very close to the mirror, the image becomes erect and magnified.
Q8. Hold a magnifying glass over text and identify the distance where you can see the text bigger than they are written. Now move it away from the text. What do you notice? Which type of lens is a magnifying glass?
Answer:
A magnifying glass is a convex lens. When held close to the text, it magnifies the text (enlarged and erect). When moved farther away, the text becomes inverted and may appear smaller or blurry.
Q9. Match the entries in Column I with those in Column II.
| Column I | Column II |
|---|---|
| (i) Concave mirror | (a) Spherical mirror with a reflecting surface that curves inwards. |
| (ii) Convex mirror | (b) It forms an image which is always erect and diminished in size. |
| (iii) Convex lens | (c) Object placed behind it may appear inverted at some distance. |
| (iv) Concave lens | (d) Object placed behind it always appears diminished in size. |
Answer:
(i) Concave mirror → (a) Spherical mirror with a reflecting surface that curves inwards.
(ii) Convex mirror → (b) It forms an image which is always erect and diminished in size.
(iii) Convex lens → (c) Object placed behind it may appear inverted at some distance.
(iv) Concave lens → (d) Object placed behind it always appears diminished in size.
Q10. The following question is based on Assertion/Reason. Assertion: Convex mirrors are preferred for observing the traffic behind us. Reason: Convex mirrors provide a significantly larger view area than plane mirrors. Choose the correct option: (i) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion. (ii) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion. (iii) Assertion is correct but Reason is incorrect. (iv) Both Assertion and Reason are incorrect.
Answer:
Answer: (i) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
Convex mirrors provide a wider field of view, making them ideal for side-view mirrors and traffic monitoring.
Q11. In Fig. 10.27, note that O stands for object, M for mirror, and I for image. Which of the following statements is true? (i) Figure (a) indicates a plane mirror and Figure (b) indicates a concave mirror. (ii) Figure (a) indicates a convex mirror and Figure (b) indicates a concave mirror. (iii) Figure (a) indicates a concave mirror and Figure (b) indicates a convex mirror. (iv) Figure (a) indicates a plane mirror and Figure (b) indicates a convex mirror. 
Answer:
Answer: (i) Figure (a) indicates a plane mirror and Figure (b) indicates a concave mirror.
In Figure (a), the image is the same size and behind the mirror (plane mirror). In Figure (b), the image is inverted and in front of the mirror (concave mirror).
Q12. Place a pencil behind a transparent glass tumbler (Fig. 10.28a). Now fill the tumbler halfway with water (Fig. 10.28b). How does the pencil appear when viewed through the water? Explain why its shape appears changed. 
Answer:
The pencil appears bent or broken at the water level. This happens because light rays bend (refract) when they pass from water to air, creating a visual illusion. The water acts like a convex lens, causing the pencil to appear displaced.
Discover, Design, and Debate
Q1. Visit a nearby hospital or the clinic of an ENT specialist, or a dentist, with your teacher or parents. Request the doctor to show you the mirrors used for examining ear, nose, throat, and teeth. Identify the kind of mirror used in these instruments. Harnessing sunlight is key to solving future energy challenges. In devices like solar cookers (Fig. 10.29), mirrors are used to converge sunlight and generate heat. In India, such designs are used in villages, thus saving electricity and reducing fossil fuel use. Think of a design for a solar cooker for your school or home and prepare a detailed proposal for it including the budget required. Use online tools or animation to do virtual experiments with spherical mirrors and lenses. Move objects in the simulation and observe how the image changes. 
Answer:
ENT/Dentist mirrors: Dentists use concave mirrors to get enlarged images of teeth. ENT specialists may use mirrors with different shapes depending on the examination.
Solar cooker design: Students can propose a design using concave mirrors or a box-type solar cooker with reflectors to concentrate sunlight. They can include materials like aluminium foil, glass, and a black cooking pot.
Virtual experiments: Students can explore online simulations (like PhET simulations) to study how images change with different mirrors and lenses.