Question

write a lab activity to find local length of the lenses​

Answer 1

Answer:

i) Place the convex lens on a 'V' stand. . ii) Light a candle and take it far away from the lens along the principal axis. iii) Adjust the screen on the other side of the lens to get a clear image on it. iv) Measure the distance between the 'V' stand and the screen which gives a rough idea of focal length of the lens.

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Answer 2

To determine focal length of a given concave mirror :-

Materials Required  :-

• A concave mirror
• A measuring scale
• A screen holder
• A mirror holder
• A mirror stand

Procedure  :-

• The distance between the selected distinct object should be more than 50 ft.
• The concave mirror placed on the mirror stand and the distant object should be facing each other.
• The screen should be placed in front of the reflecting surface of the mirror. To obtain a clear, sharp image the screen should be adjusted.
• Using a meter scale the distance between the concave mirror and screen can be determined. The distance is the same as the focal length of the given concave mirror.
• Repeat the above procedure thrice to calculate the average focal length.

To determine focal length of a convex lens :-

Materials Required

• A wooden bench
• A convex lens
• A lens holder
• A screen fixed to a stand
• A measuring scale

Procedure

• Without disturbing the lens and screen, arrange both of them on the wooden bench.
• Place the lens on the holder facing a distant object.
• Place the holder with the screen on the bench.
• The position of the screen should be such that the sharp image of the distant object is obtained on it.
• The difference between the position of the lens and the screen is equal to the focal length of the given convex lens.
• Now shift the focus to towards various other distant object and calculate the focal length of the convex lens.