﻿ Numericals on Light Class 10 Science # Numerical on Light Class 10

QUESTIONS: (3 marks each)
Question 1.
A coin placed at the bottom of a tank appears to be raised when water is poured into it. Explain.

Question 2.
A 5 cm tall object is placed perpendicular to the principal axis of a convex lens of focal- length 20 cm. The distance of the object from the lens is 30 cm. Find the:
(i) position
(ii) nature
(iii)  size of the image formed.

Question 3.
(a) Write two rules of the new Cartesian sign conventions for spherical mirrors.
(b) Trace the path of the reflected ray by drawing a figure if it passes from centre of curvature of a concave mirror.

Question 4.
Design an activity using concave mirror to prove that it s converging in nature. Also state a method to find its rough focal length.

Question 5.
4.5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Give the location of image and magnification. Describe what happens to the image as the needle is moved farther from the mirror.

Question 6.
Rohit placed a pencil perpendicular to principal axis in front of a converging mirror of focal length 30 cm. The image formed is twice the size of the pencil. Calculate the distance of the object from the mirror.

Question 7.
Define magnification produced by a spherical mirror in terms of height of a object and image. How is it related to object and image distance? Explain why magnification is positive for virtual image and negative for real image?

Question 8.
An object is placed at a distance of 25 cm away from a converging mirror of focal length 20 cm. Discus the effect on the nature and position of the image if the position of the object changes from 25 cm to 15 cm. Justify your answer without using mirror formula.

Question 9.
Write one similarity and one dissimilarity between image formed by pane mirror and convex mirror.

Question 10.
(a) State Snell’s law of refraction.
(b) When a ray of light travelling in air enters obliquely into a glass slab, it is observed that the light ray emerges parallel to the incident ray but it is shifted sideways slightly. Draw a ray diagram to illustrate it.

Question 11.
A 5cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 10 cm. The distance of the object from the lens is 15 cm. Find the nature, position and size of the image. Also find its magnification.

Question 12.
One half of a convex lens is covered with a black paper.
(a)Show the formation of image of an object placed at 2F1, of such covered lens with the help of ray diagram. Mention the position and nature of image.
(b)Draw the ray diagram for same object at same position in front of the same lens, but now uncovered. Will there be any difference in the image obtained in the two cases? Give reason for your answer.

Question 13.
(a) The refractive index of Ruby is 1.71. What is meant by this statement?
(b) The refractive index of some medium are given below:
Crown glass- 1.52
Water- 1.33
Sapphire- 1.77
In which of the medium is the speed of light
(i)maximum
(ii)minimum
(iii) Calculate speed of light in sapphire.

Question 14.
A 10 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 30 cm. The distance of the object from the lens is 20 cm. Find the:
(a)Position
(b)Nature
(c)Size of the image formed.

Question 15.
Draw a ray diagram to show refraction of light through a glass slab and label on it the following:
(i)Incident ray
(ii)Refracted ray
(iii)Emergent ray
(iv)Lateral shift (displacement)
Question 16.
If the image formed by mirror for all positions of the object placed in front of it is always virtual and diminished, state the type of the mirror. Draw a ray diagram in support of your answer. Where are such mirrors commonly used and why?

Question 17.
A 6 cm object is placed perpendicular to the principal axis of a convex lens of focal length 15 cm. The distance of the object from the lens is 10 cm. Find the position, size and nature of the image formed, using the lens formula.

### Practice Question

Question 1 Which among the following is not a base?
A) NaOH
B) $NH_4OH$
C) $C_2H_5OH$
D) KOH
Question 2 What is the minimum resistance which can be made using five resistors each of 1/2 Ohm?
A) 1/10 Ohm
B) 1/25 ohm
C) 10 ohm
D) 2 ohm
Question 3 Which of the following statement is incorrect? ?
A) For every hormone there is a gene
B) For production of every enzyme there is a gene
C) For every molecule of fat there is a gene
D) For every protein there is a gene