Question

A needle placed 45 cm from a lens forms an image on the screen placed 90 cm on the other side of the lens identify the type of the lens and determine its focal length what is the size of the image If the size of needle is 5 cm ?

Answer 1

ANSWERS :-


$solution$

HERE,

U = -45 CM

V = 90 CM

F = ?


⚡⚡WE USE LENS FORMULA TO CALCULATE FOCAL LENGTH :-

from

1/f = 1/v - 1/u

1/f = 1/90 + 1/45 = 1+2/90 = 3/90

1/f = 3/90

1/f = 1/30

f = 30 cm

As f is positive , the lens must be convex.

from

h2/h1 = v/u

h2 = h1 * v/u

= 5 * 90 /-45

= -10cm


As h2 is negative, the image is inverted.

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❤BE BRAINLY ❤

Answer 2

Answer

Please refer to the attachment

Explanation: