The focal length of a concave mirror is 10 cm. Object placed at 20 cm gives image distance MCQ with Answer and Explanation
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Question #1
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TIR requires light travel from:
Correct Answer: Option A
Explanation:
TIR: denser→rarer medium AND incidence angle > critical angle. Glass to air satisfies first condition; angle must exceed θ_c. Memory aid: 'TIR: n₁>n₂ AND i>θ_c; direction matters'. Optics condition frequently tested in competitive exams.
TIR: denser→rarer medium AND incidence angle > critical angle. Glass to air satisfies first condition; angle must exceed θ_c. Memory aid: 'TIR: n₁>n₂ AND i>θ_c; direction matters'. Optics condition frequently tested in competitive exams.
Question #2
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The device that protects electrical circuits from overload is
Question #3
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A convex lens forms a real image of an object. If the lower half of the lens is covered, the image will:
Correct Answer: Option A
Explanation:
Covering part of a lens reduces the amount of light reaching the image, making it fainter, but the entire image is still formed because light from each object point can pass through the uncovered portion and converge to the corresponding image point. Image position, size, and nature remain unchanged. Memory aid: 'Partial lens coverage ⇒ reduced intensity, not partial image'. This conceptual question tests understanding of image formation principles, commonly featured in competitive exams to identify misconceptions about ray optics. Always recall that every point on lens contributes to entire image.
Covering part of a lens reduces the amount of light reaching the image, making it fainter, but the entire image is still formed because light from each object point can pass through the uncovered portion and converge to the corresponding image point. Image position, size, and nature remain unchanged. Memory aid: 'Partial lens coverage ⇒ reduced intensity, not partial image'. This conceptual question tests understanding of image formation principles, commonly featured in competitive exams to identify misconceptions about ray optics. Always recall that every point on lens contributes to entire image.
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