Questions-Refraction of light at Curved Surfaces Questions

 

Refraction of light at curved surfaces

1/2 Mark Questions

1. Write the lens formula.

Ans: Lens formula 1/f =  1/v - 1/ u.

2. Which image can be captured on a screen ?

Ans: Real

3. Which lens always form virtual images?

Ans: Concave

4. Which lens can form real and virtual images?

Ans: Convex

5. What happens to a ray that travels along the principal axis? 

Ans: Any ray passing along the principal axis is undeviated.

6. What happens to a ray that travels through the optic centre ?

Ans: Any ray passing through the optic centre is undeviated.

7. What happens to a ray travelling parallel to the principal axis?

Ans: The rays passing parallel to the principal axis converge at the focus or appear to diverge from the focus.

8. What happens to the light ray when a transparent material with two curved surfaces is placed in its path ?

Ans: The light ray gets refracted two times.

9. Define Paraxial rays.

Ans: The rays which are close to the principal axis are called paraxial rays.

10.The lens which always form virtual images is [ ]

 A) Convex B) Concave C) plano-convex D) Concavo convex 

Ans:B) Concave 

11.If the focal length is positive then the lens is ---------- [ ]

 A) Convex B) Concave C) plano-convex D) Concavo convex

Ans: A) Convex

12. Which lens acts as converging lens?

Ans: Bi-convex lens

13. The rays from the distant object, falling on the convex lens pass through

 A) Pole B) Centre of curvature C) Focus D) Focal length

Ans: C) Focus

14. If the rays move very close to the principal axis, the rays can be treated as parallel and are called ---------- rays.

 A) Focal rays B) parallel rays C) Un-deviated rays D) Paraxial rays

Ans: D) Paraxial rays

15. The ray passing through the ---------- of the lens is not deviated.

 A) Pole B) Centre of curvature C) Focus D) A and B

Ans: D) A and B

16. On what factors does the focal length of a lens depends? 

A) Radius of curvature B) Material C) Surrounding medium D) All above

Ans: D) All above

17. ---------- is not the property of a concave lens?

 A) It is thicker at the edges and tapering in the middle 

B) It forms virtual and erect image

C) It forms enlarged image 

D) It forms diminished image

Ans: C) It forms enlarged image

18. According to this law, a light ray which travels along the normal drawn to a curved surface does not deviate from its path

 A) Snell's law B) Fermat's principle C) Newton's laws D) All the above

Ans: B) Fermat's principle

19. An object is placed at a distance of 20 cm. in front of a convex lens whose radius of curvature is 40 cm. The image is formed at ----------

 A) Beyond 'C' B) Between 'C' and 'F' C) At 'C' D) At infinite distance

Ans: D) At infinite distance

20. An object is placed at a distance of 40 cm. infront of a convex lens of focal length 20 cm. The image is formed at a distance of

 A) 40 cm B) 20 cm C) ∞ D) 40/3 cm

Ans: A) 40 cm

21. A real and inverted image of the same size is formed by a convex lens, when the object is placed ----------

 A) at F B) at C C) between F and C D) between F and optical centre

Ans: B) at C

22. Where should be the object placed on the principal axis of a convex lens in order to get virtual image?

Ans: A) between optic centre and F 

1 Mark Questions

1. Write the lens formula and explain the terms in it.

Ans: Lens formula

 1/f=1/v - 1/u

u - object distance

v - image distance

f - focal length of the lens

2. Define focal length of lens.

Ans: The distance between the focal point and optic centre is called the focal length of lens (f).

3. What is lens?

Ans: Lens : A lens is madeup of a transparent material, which has atleast two curved surfaces.

4. How does a light ray behave when it is passing through the focus of a lens?

Ans: When a light ray passing through the focus, will take a path parallel to the principal axis after refraction.

5. How does the lens form an image?

Ans: The lens forms an image through converging light rays or diverging light rays.

6. If we allow a light ray to pass through the focus, which path does it take?

Ans: The ray passing through the focus will take a path parallel to principal axis after refraction.

7. What happens when parallel rays of light fall on a lens making some angle with the principal axis?

Ans: The rays converge at a point or appear to diverge from a point lying on the focal plane.