Optics - Ray Optics
Q. A plane mirror produces an image that is: (2023)
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A.
Real and inverted
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B.
Virtual and erect
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C.
Real and erect
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D.
Virtual and inverted
Solution
A plane mirror always produces a virtual and erect image, which is the same size as the object.
Correct Answer: B — Virtual and erect
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Q. If the radius of curvature of a convex mirror is 20 cm, what is its focal length? (2022)
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A.
10 cm
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B.
20 cm
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C.
30 cm
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D.
40 cm
Solution
The focal length (f) of a mirror is given by f = R/2. For a convex mirror, R is positive, so f = 20 cm / 2 = 10 cm.
Correct Answer: A — 10 cm
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Q. In a concave lens, the focal length is: (2023)
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A.
Positive
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B.
Negative
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C.
Zero
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D.
Infinite
Solution
The focal length of a concave lens is negative, indicating that it diverges light rays.
Correct Answer: B — Negative
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Q. The critical angle for total internal reflection occurs when light travels from: (2019)
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A.
Air to water
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B.
Water to air
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C.
Glass to air
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D.
Air to glass
Solution
The critical angle occurs when light travels from a denser medium (water) to a less dense medium (air).
Correct Answer: B — Water to air
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Q. What happens to the image distance when the object is moved closer to a concave mirror? (2021)
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A.
Increases
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B.
Decreases
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C.
Remains the same
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D.
Becomes negative
Solution
As the object moves closer to a concave mirror, the image distance increases, and the image becomes larger and more distant.
Correct Answer: A — Increases
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