Three students measured the focal length of a convex lens using parallel rays from a distant object- All of them measured the distance between the lens and the inverted image on the screen-i Student A saw a sharp image on the screen and labelled the distance as f1ii Student B saw a slightly larger blurred image on the screen and labelled the distance as f2iii Student C saw slightly smaller blurred image on the screen and labelled the distance as f3The relation between the three measurements would most likely be1 f1-f2-f32 f1-f2-f33 f3-f1-f24 f1-f2 and f1-f3

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Byju's Answer

Standard X

Physics

Linear Magnification

Three student...

Question

Three students measured the focal length of a convex lens using parallel rays from a distant object. All of them measured the distance between the lens and the inverted image on the screen.
(i) Student A saw a sharp image on the screen and labelled the distance as f₁
(ii) Student B saw a slightly larger blurred image on the screen and labelled the distance as f₂
(iii) Student C saw slightly smaller blurred image on the screen and labelled the distance as f₃

The relation between the three measurements would most likely be
(1) f₁ = f₂ = f₃
(2) f₁ < f₂ < f₃
(3) f₃ < f₁ < f₂
(4) f₁ < f₂ and f₁ = f₃

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Solution

A convex mirror converges all the rays coming from the distant object on its focus. According to given conditions, we can say if a sharp image is obtained at f₁, then f₁ must be the focal point of the lens. Now if the distance between the screen and the lens is varied then beyond the focus f₁, the image obtained would be large and blurred and behind the focus f_1,the image would be smaller and blurred.

Hence, the correct answer is option 3.

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