Light reflection and refraction Worksheet-19

Light reflection and refraction Worksheet-19

1. Show the formation of image of the object AB with the help of suitable rays.

2. Show the formation of image with the help of suitable rays.

3. Why does a ray of light bend when it travels from one medium to another?

4. Complete the figure for the path of ray of light beyond the lens.

5. Complete the path of the rays.

6. Complete the path of the ray.

7. Give the characteristics of image formed by a plane mirror.

8. An object is placed at 0.06 m from a convex lens of focal length 0.1 m. Calculate the position of the image?

9. An object is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position and nature of the image.

10. Light enters from air into diamond, which has a refractive index of 2.42. Calculate the speed of light in diamond. The speed of light in air is  3 × 10⁸ ms^–1

Answer:

1. The course of rays for the formation of image of object AB is shown in the figure. The image A' B' is real, inverted and magnified.

2. The course of rays for the formation of image of object AB is shown in Fig. The image A'B" is real, inverted and of the same size as the object.

3. Different media have different optical density. Therefore, velocity of light in different media is different. That is why a ray of light bends when it travels from one medium to another.

4. A ray of light incident on the convex lens in a direction parallel to the principal axis passes actually through the principal focus F of the lens on the other side as shown in Fig.

5. On passing through the concave lens, the given ray diverges and appears to come from principal focus F of the lens on the side as shown in the figure

6. The ray incident on the concave lens in a direction parallel to principal axis diverges on passing through the lens, appearing to come from principal focus F of the lens on left side as shown in the figure.

7. The image formed by a plane mirror is virtual, erect and of the same size and at the same distance at the back of the mirror as the object is in front of the mirror. The image is laterally inverted.

8. Here, u = –0.06 m = –6 cm

          f = 0.1 m = 10 cm, v = ?

As    

          v = –15 cm

Negative sign of v shows that the image is virtual, being on the same side of the lens as the object is.

9. Here, object distance, u = –20 cm

Radius of curvature, R = 30 cm

Image distance, v = ?

As            ∴

As v is positive, image is at the back of the mirror.

It must be virtual and erect.

10. Here, n = 2.42,   v = ?, c = 3 × 10⁸ m/s.

As    

∴ = 1.24 × 10⁸ m/s^–1