Question 1

Draw the reflected ray in each case (Use a ruler and protractor for accurate drawing). What is the angle of reflection in each case?

Cases:
(i) The mirror is not tilted and the light ray falls along the normal to the mirror surface.
(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.

Accepted Answer

Solution:
(i) When the mirror is not tilted and the light ray falls along the normal, the angle of incidence is 0°. According to the law of reflection, angle of reflection = angle of incidence = 0°. So the reflected ray will retrace the path of the incident ray.

(ii) When the mirror is tilted but the light ray still falls along the normal to the tilted surface, the angle of incidence is again 0°. Hence, angle of reflection = 0°. The reflected ray retraces the incident ray.

(iii) When the mirror is tilted and the light ray falls at 20° from the normal, the angle of incidence is 20°. According to the law of reflection, angle of reflection = 20°. The reflected ray will be drawn at 20° on the other side of the normal.

In all cases, use a protractor to measure the angles and a ruler to draw the rays accurately. — The law of reflection states that the angle of incidence equals the angle of reflection. When the ray falls along the normal, the angle of incidence is 0°, so the reflected ray retraces the incident ray. When the mirror is tilted and the ray falls at an angle to the normal, the angle of reflection equals the angle of incidence, so the reflected ray is drawn symmetrically on the other side of the normal.

Question 2

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.

Images:
(i)
(ii)
(iii)

Accepted Answer

Solution:
(i) The image formed is of the same size and upright, indicating a plane mirror.
(ii) The image is diminished and upright, indicating a convex mirror.
(iii) The image is magnified and inverted or real, indicating a concave mirror.

Therefore, the matches are:
(i) Plane mirror
(ii) Convex mirror
(iii) Concave mirror — Plane mirrors form images that are virtual, upright, and of the same size. Convex mirrors form virtual, upright, and diminished images. Concave mirrors can form magnified and inverted images depending on the object's position.

Question 3

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.

Images:
(i)
(ii)
(iii)

Accepted Answer

Solution:
(i) The image is of the same size and not magnified or diminished, indicating flat transparent glass.
(ii) The image is magnified and erect, indicating a convex lens.
(iii) The image is diminished and erect, indicating a concave lens.

Therefore, the matches are:
(i) Flat transparent glass piece
(ii) Convex lens
(iii) Concave lens — Flat glass does not change the size of the image. Convex lenses converge light and can magnify images. Concave lenses diverge light and diminish the size of images.

Question 4

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

Accepted Answer

Correct option: (ii) Angle of incidence is 0°.

Explanation:
When light is incident along the normal to the mirror surface, the angle between the incident ray and the normal is 0°. Therefore, the angle of incidence is 0°, and by the law of reflection, the angle of reflection is also 0°. Hence, the reflected ray retraces the path of the incident ray. — The angle of incidence is measured between the incident ray and the normal. If the light falls along the normal, this angle is 0°, not 90°. Reflection still takes place with angle of reflection equal to 0°.

Question 5

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.

Accepted Answer

Solution:
Observe the images formed in each mirror:
- The mirror forming an image of the graph sheet that is of the same size and upright is the plane mirror.
- The mirror forming a diminished, virtual, and upright image is the convex mirror.
- The mirror forming a magnified or inverted image is the concave mirror.

Label the mirrors accordingly in the figure. — Plane mirrors form virtual, upright, and same-size images. Convex mirrors form virtual, upright, and diminished images. Concave mirrors can form magnified or inverted images depending on object position.

Question 6

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.

Accepted Answer

Correct option: (iii) her inverted image keeps increasing in size and eventually it becomes erect and magnified.

Explanation:
As the woman moves towards the concave mirror from beyond the center of curvature towards the focus, the image formed changes from diminished and inverted to magnified and inverted. When she moves closer than the focus, the image becomes virtual, erect, and magnified. — Concave mirrors form real, inverted images when the object is beyond the focus. As the object moves closer to the mirror, the image size increases and eventually becomes virtual and erect when the object is within the focal length.

Question 7

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?

Accepted Answer

Solution:
When the magnifying glass (a convex lens) is held close to the text, the text appears larger because the lens forms a magnified virtual image when the object is within the focal length. As you move the lens away, the image size decreases and eventually becomes smaller or blurry.

A magnifying glass is a convex lens. — A convex lens converges light rays and can form magnified virtual images when the object is within its focal length. This property is used in magnifying glasses to enlarge the appearance of objects.

Question 8

Match the entries in Column I with those in Column II.

Column I:
(i) Concave mirror
(ii) Convex mirror
(iii) Convex lens
(iv) Concave lens

Column II:
(a) Spherical mirror with a reflecting surface that curves inwards.
(b) It forms an image which is always erect and diminished in size.
(c) Object placed behind it may appear inverted at some distance.
(d) Object placed behind it always appears diminished in size.

Accepted Answer

Solution:
(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. — Concave mirrors curve inward and can form real or virtual images. Convex mirrors curve outward and always form virtual, erect, and diminished images. Convex lenses can form inverted images when the object is beyond the focal length. Concave lenses always form virtual, erect, and diminished images.

Question 9

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.

Accepted Answer

Correct option: (i) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.

Explanation:
Convex mirrors are preferred for observing traffic behind because they provide a wider field of view compared to plane mirrors. This allows the driver to see more area behind the vehicle, enhancing safety. — Convex mirrors diverge light rays and thus cover a larger area in the reflected image. This property makes them suitable for rear-view mirrors in vehicles.

Question 10

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.

Accepted Answer

Correct option: (A) Figure (a) indicates a plane mirror and Figure (b) indicates a concave mirror.

Explanation:
In Figure (a), the image is virtual, upright, and of the same size as the object, characteristic of a plane mirror.
In Figure (b), the image is real and inverted, characteristic of a concave mirror when the object is beyond the focus. — Plane mirrors form virtual, upright, and same-size images. Concave mirrors can form real, inverted images when the object is beyond the focal point.

Question 11

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.

Accepted Answer

Solution:
When the tumbler is empty, the pencil appears straight. After filling the tumbler halfway with water, the pencil appears bent or broken at the water surface.

Explanation:
This happens due to refraction of light. Light rays coming from the pencil bend when they pass from water to air because of the change in medium and speed of light. This bending causes the pencil to appear displaced or bent at the water surface. — Refraction occurs when light passes from one medium to another with different optical density, changing its speed and direction. This causes objects partially submerged in water to appear bent or broken.

Question 12

Which type of spherical mirror has its reflecting surface curved inward, resembling the inner surface of a hollow glass sphere?

Accepted Answer

Concave mirror — A concave mirror has its reflecting surface curved inward, like the inner surface of a hollow glass sphere. This inward curvature causes light rays to converge upon reflection.

Question 13

When you look at the inner side of a shiny metallic spoon, what kind of image do you observe?

Accepted Answer

Inverted and enlarged image — The inner side of a spoon acts as a concave mirror, producing an inverted and enlarged image when the object is close to the mirror.

Question 14

What is the shape of the reflecting surface of a convex mirror?

Accepted Answer

Curved outward — A convex mirror has its reflecting surface curved outward, like the outer surface of a hollow sphere, causing light rays to diverge after reflection.

Question 15

How are spherical mirrors made if they are not sliced from a hollow glass sphere?

Accepted Answer

Spherical mirrors are made by grinding and polishing a flat glass piece into a curved surface and then applying a reflective coating on it. — Spherical mirrors are created by shaping a flat glass piece into a curved surface through grinding and polishing. Then, a reflective coating such as aluminium is applied either on the outer or inner curved surface to form concave or convex mirrors respectively.

Light: Mirrors and Lenses

Light: Mirrors and Lenses — Study Notes

Light: Mirrors and Lenses

10.1 What Are Spherical Mirrors?

10.2 What Are the Characteristics of Images Formed by Spherical Mirrors?

Practice Questions — Light: Mirrors and Lenses

Light: Mirrors and Lenses — Study Guides & Articles

All 13 Chapters in Curiosity