Optical Instruments — Flashcards
ICSE · Class 12 · Physics
34 flashcards for Optical Instruments (ICSE Class 12 Physics) to test yourself on key terms and facts. Part of the ICSE Class 12 Physics syllabus.
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State the power of accommodation of the eye.
Answer
Power of accommodation is the ability of the eye lens to change its focal length by the action of ciliary muscles so that both near and distant objects are focused on the retina.
What is the least distance of distinct vision?
Answer
The least distance of distinct vision is the nearest distance up to which the eye can see clearly by applying maximum power of accommodation. For a normal eye, it is 25 cm.
Why does an object look bigger when it subtends a larger visual angle?
Answer
The apparent size of an object depends on the visual angle at the eye. A larger visual angle means the image formed on the retina is larger, so the object appears bigger.
A small object is placed at a distance of 25 cm from the eye. Why is this distance special?
Answer
This distance is the least distance of distinct vision for a normal eye. At this distance the eye can see clearly with maximum accommodation. If the object is placed closer than 25 cm, it cannot be se…
State the magnifying power of a simple microscope when the image is formed at the least distance of distinct vision.
Answer
Formula: M = 1 + D/f Where D is the least distance of distinct vision and f is the focal length of the lens. Meaning: smaller focal length gives larger magnifying power.
A simple microscope has focal length 5 cm. Find its magnifying power for final image at 25 cm.
Answer
Given: D = 25 cm, f = 5 cm Formula: M = 1 + D/f Step 1: M = 1 + 25/5 Step 2: M = 1 + 5 Step 3: M = 6 Answer: 6…
A simple microscope has focal length 10 cm. Find its magnifying power when the image is at infinity.
Answer
Given: D = 25 cm, f = 10 cm Formula: M = D/f Step 1: M = 25/10 Step 2: M = 2.5 Answer: 2.5…
Why does keeping the eye very close to a simple microscope increase magnifying power?
Answer
If the eye is moved away from the lens, the image subtends a smaller angle at the eye and magnifying power decreases. Keeping the eye close to the lens gives the maximum visual angle and maximum magni…
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