English Medium कक्षा १० - CBSE Important Questions for Science

List four characteristics of the image formed by a concave lens of focal length 20 cm when the object is placed at a distance of 40 cm from its optical centre. 

The size of image of an object by a convex lens of focal length 20 cm is observed to be reduced to  `1/3` rd of its size . Find the distance of the object from the optical centre of the lens . 

List in proper sequence the steps of the experiment for determining the approximate focal length of a given concave mirror by obtaining the image of a distant object.

A real image is formed by the light rays after reflection or refraction when they:

1. actually meet or intersect with each other.
2. actually converge at a point.
3. appear to meet when they are produced in the backward direction.
4. appear to diverge from a point.

Which of the above statements are correct?

Answer the following question.
Write the modification in the curvature of the eye lens which enables us to see the nearby objects clearly?

In torches, search lights and headlights of vehicles the bulb is placed ______.

Rohit wants to have an erect image of an object using a converging mirror of focal length 40 cm.

1. Specify the range of distance where the object can be placed in front of the mirror. Justify.
2. Draw a ray diagram to show image formation in this case.
3. State one use of the mirror based on the above kind of image formation.

An object is kept at a distance of 1m from a lens of power +2D:

1. Identify the type of lens.
2. Calculate its focal length and distance of the image formed.

A 10 cm long pencil is placed 5 cm in front of a concave mirror having a radius of curvature of 40 cm.

1. Determine the position of the image formed by this mirror.
2. What is the size of the image?
3. Draw a ray diagram to show the formation of the image as mentioned in part (i).

In the following ray diagram the correctly marked angle are:

(a) ∠i and ∠e

(b)  ∠A and ∠D

(c) ∠i, ∠e and ∠D

(d) ∠r, ∠A and ∠D

A person needs a lens of power -5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision and (ii) near vision?

The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?

What happens to the image distance in the eye when we increase the distance of an object from the eye?

A person is unable to read a book placed closer than 1 meter from his eyes. Identify the defect of vision in his eyes. Draw the ray diagrams to show the defect of vision and its correction.

In the following diagram, the correctly marked angles are

(A) All
(B) Only ∠i and ∠A
(C) ∠i, ∠r and ∠A
(D) ∠i, ∠A and ∠D

In an experiment to trace the path of a ray of light through a triangular glass prism, a student would observe that the emergent ray

(a) is parallel to the incident ray.

(b) is along the same direction of incident ray.

(c) gets deviated and bends towards the thinner part of the prism.

(d) gets deviated and bends towards the thicker part (base) of the prism.

In which of the following four diagrams is the correct path of a ray of light passing through a glass prism shown ?

State one role of ciliary muscles in the human eye.

Draw a labeled ray diagram to illustrate the dispersion of a narrow beam of white light when it passes through a glass prism.

An old man cannot see objects closer than 1 m from the eye clearly. Name the defect of vision he is suffering from. How can it be corrected? Draw ray diagram for the (i) defect of vision and also (ii) for its correction.