1. OBJECTIVE QUESTIONS
FOR
NEET AIIMS JIPMER

2. PHYSICS RAY OPTICS SET 2 MCQ’S

3. Q1. The focal length of a convex lens depends upon :
Frequency of the light ray
Wavelength of the light ray
Both (A) and (B)
None of these

4. ANSWER (C) EXPLANATION
1 𝑓 =(𝜇−1) 1 𝑅 1 − 1 𝑅 2
Refractive index ‘𝜇 ′ depends on the both wavelength and frequency of light.

5. Q2. A convergent lens placed inside a vessel filled with liquid is shown in the figure below. The lens has focal length +20 cm when in air, and its material has refractive index 1.5. if the liquid has refractive index 1.6, the focal length of the system is
+80 cm
-80 cm
-160 cm
-100 cm

6. ANSWER (C) EXPLANATION

7. Q3. A 1.7 m tall person stands 1.6 m in front of a vertical plane mirror. The height of his image will be :
1.6 m
1.7 m
0.85 m
3.4 m

8. ANSWER (B) EXPLANATION
Image formed will be of the same size as object. (properties of image formed by a plane mirror).

9. Q4. A convergent lens is placed inside a vessel filled with liquid
Q4. A convergent lens is placed inside a vessel filled with liquid. The lens has focal length +20 cm when in air, and its material has refractive index 1.5. if the liquid has refractive index 1.33, the new focal length of the lens is :
+ 80 cm
– 80 cm
–160 cm
–100 cm

10. ANSWER (A) EXPLANATION

11. Q5. A plane glass slab is kept over various coloured letters
Q5. A plane glass slab is kept over various coloured letters. The letter which appears least raised is :
Blue
Violet
Green
Red

12. ANSWER (D) EXPLANATION

13. Q6.The sun (diameter = D) subtends angle 𝜽 radians at the pole of a concave mirror of focal length f . The diameter of the image of the sun formed by the mirror is :
f 𝜃
2f 𝜃
f2 𝜃/D
D 𝜃

14. ANSWER (A) EXPLANATION
Since the image formed at the focus is circular and the angle subtended at the pole is 𝜃.
∴ Diameter of the image = f 𝜃.

15. Q7. A light beam passes from air into liquid and is deviated by 150 when the angle of incidence is 600. What is the index of refraction of the liquid ?
𝟐 𝟑
𝟑 𝟐
𝟐 𝟑
𝟑 𝟐

16. ANSWER (D) EXPLANATION
When the ray deviates by 15o, then,

17. Q8. A lens is placed between a source of light and a wall
Q8. A lens is placed between a source of light and a wall. It forms images of area A1 and A2 on the wall, for its two different position. The area of source is :

18. ANSWER (C) EXPLANATION
we have, object size

19. Q9. which source is associated with a line emission spectrum ?
Red traffic light
Sun
Electric fire
Neon street light

20. ANSWER (D) EXPLANATION
Neon lights are a type of cold cathode gas-discharge light. A neon tube light is a sealed glass tube with a metal electrode at each end, filled with one of a number of gases at low pressure.
A high potential of several thousand volts applied to the electrodes ionizes the gas in the tube, causing it to emit colored light. The color of the light depends on the gas in the tube.
Neon lights were named for neon, a noble gas which gives off a popular orange light, but other gases and chemicals are used to produce other colors, such as hydrogen (red), helium (yellow), carbon dioxide (white), and mercury (blue).

21. Q10. How should people wearing their spectacles work with a microscope ?
They should keep on wearing their spectacles
They should take off their spectacles
They may either put on their spectacles or they may take off their spectacles; it makes no difference
They cannot use the microscope at all

22. ANSWER (b) EXPLANATION
As the defect of eye can be rectified by adjusting the microscope, they should take off their spectacles.

23. Q11. A mark ‘A’ placed on the surface of a glass sphere is viewed through glass from a point directly opposite, Radius of sphere = 10 cm. Refractive index of glass is 1.5. Which one of the following statements is correct ?
The image formed is real and at a distance of 0.4 m from the eye
The image formed is virtual and at a distance of 0.2 m from the eye
The image formed is virtual and at a distance 0.3 m from the centre of the sphere
The image formed is real and at a distance of 0.2 m from point A

24. ANSWER (C) EXPLANATION

25. Q12. Immiscible transparent liquids A, B, C, D and E are placed in rectangular container of glass with the liquids making layers according to their densities. The refractive index of the liquids is shown in the following figure. The container is illuminated from the side and a small piece of glass having refractive index 1.61 is gently dropped into the liquid layers. The glass piece, as it descends downwards, will not be visible in (refer figure):
Liquid A and B only
Liquid C only
Liquid D and E
Liquid A, B, D and E

26. ANSWER (B) EXPLANATION
Glass piece will not be visible in the layer having the same value of refractive index as that of glass piece i.e. the layer C

27. Q13. A convex lens of glass is immersed in water compared to its power in air, its power in water will :
Diminish
Increase
Remain the same
Diminish for red light and increase for blue light

28. ANSWER (A) EXPLANATION

29. Q14. The focal length of a convex lens is 30 cm and the size of the image is half of the object. The object distance is :
60 cm
90 cm
30 cm
40 cm

30. ANSWER (B) EXPLANATION

31. Q15. A lens behaves as a converging lens in air and a diverging lens in water. The refractive index of the material is -
Equal to unity
Equal to 1.33
Between unity and 1.33
Greater than 1.33

32. ANSWER (C) EXPLANATION
Between unity and 1.33, because refractive index of water is 1.33.

33. Q16. In the displacement method of finding focal length of a convex lens, I1 and I2 are the sizes of the images respectively for the two position of the lens. The size of the object is :

34. ANSWER (C) EXPLANATION
𝑂= 𝐼 1 𝐼 2

35. Q17. fv and fR are the focal length of a convex lens for violet and red light, respectively, and Fv and FR are the focal length of a concave lens for violet and red light, respectively. Which one of the following relations is correct ?
f v < f R and F V > F R
f v > f R and F V < F R
f v < f R and F V < F R
f v > f R and F V > F R

36. ANSWER (C) EXPLANATION

37. Q18. A thin convex lens of focal length 30 cm and refractive index 1
Q18. A thin convex lens of focal length 30 cm and refractive index 1.5 is placed on a horizontal plane mirror. It is found that an object, at a height ‘h’ above the lens, has no parallax with its image. The h is :
60 cm
30 cm
45 cm
20 cm

38. ANSWER (B) EXPLANATION
When rays of light are incident normal to the plane mirror, they are rebounced back.
So if the object is at the focus of the convex lens, then after refraction through the lens, rays of light become normal to the plane mirror which makes them rebounce and form the image at the same point of the object.
It shows height of the object is equal to focal length of the convex lens i.e. 30 cm.

39. Q19. Time taken by the sunlight to pass through a window of thickness 4 mm whose refractive index is 1.5 is :
2× seconds
2× seconds
2× 10 −11 seconds
2× 10 −8 seconds

40. ANSWER (C) EXPLANATION
we have, μ= C air C medium
∴ C medium = C air μ
Time taken= Thickness of the medium Velocity of light in the medium
= Thickness ×μ C air
= 4× 10 −3 ×1.5 3× 10 8
2× 10 −11 seconds

41. Q20. Two lenses whose powers are +2D and -4D respectively are placed in contact. The power of the combination is :
– 2D
– 4D
+ 2D
+ 4D

42. ANSWER (A) EXPLANATION
𝑃= 𝑃 1 + 𝑃 2
= +2𝐷−4𝐷
=−2𝐷

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