Chapter 10 Solutions — Light: Mirrors and Lenses

Keep the Curiosity Alive

1. 1.
   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°
2. 2.
   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)…
3. 3.
   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
4. 4.
   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
5. 5.
   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
6. 6.
   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.
7. 7.
   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.
8. 8.
   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?
9. 9.
   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…
10. 10.
    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…
11. 11.
    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)…
12. 12.
    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.