StudyWithGenius

Welcome to your Chapter 9 Ray Optics and Optical Instruments MCQs

1.
A concave mirror is held in water. What should be the change in the focal length of the mirror?

2.
Two concave mirrors have the same focal length but the aperture of one is larger than that of the other. Which mirror forms the sharper image and why?

3.
A man stands in front of a mirror of special shape. He finds that his image has a very small head, a fat body, and legs of normal size. What can we say about the shapes of the three parts of the mirror?

4.
Calculate its focal length if the radii of curvature of a double convex lens are 10 cm, and 20 cm and its refractive index is 1.75.

5.
Which of the following causes dispersion?

6.
What is the relative refractive index of water with respect to glass?

7.
What will be the color of the sky in the absence of the atmosphere?

8.
On what factor does the normal shift through a refracting medium depend?

9.
A lens immersed in a transparent liquid is not visible. Under what condition can this happen?

10.
What is the cause of the blue color of the ocean?

11.
Which of the following is a necessary condition for total internal reflection?

12.
‘X’ is an optical illusion observed in deserts or over hot extended surfaces like a coal-tarred road, due to which a traveler sees a shimmering pond of water some distance ahead of him and in which the surrounding objects like trees appear inverted. Identify X.

13.
How many types of spherical refracting surfaces are there?

14.
X is thicker in the middle than at the edges, whereas, Y is thicker at the edges than in the middle. Identify ‘X’ and ‘Y’.

15.
According to the thin lens formula, which one of the following is true regarding the focal length of the lens?

16.
A lens has a focal length of 10 cm. Where the object should be placed if the image is to be 40 cm in the positive direction from the lens?

17.
Calculate the focal length of a biconvex lens if the radii of its surfaces are 50 cm and 20 cm, and index of refraction of the lens glass = 1.2.

18.
How much intensity of the image is increased if the diameter of the objective of a telescope is doubled?

19.
A fly is sitting on the objective of a telescope. What will be its effect on the final image of the distant object?

20.
How does the magnifying power of a telescope change on increasing the diameter of its objective?

Thank You