Question

(1) If your eye glass has focal length 60 cm, what is your far point?(2) A person is known to use a lens of power-(a) -5.5 D for his distant vision(b) +1.5 D for his near visionFind the focal length of the lens used for correcting his vision?(3) Find the position, nature and size of image formed by a convex lens of focal length 12 cm of an object 5 cm high placed at a distance 20 cm from it?(4) A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of lens.Please fast...Give me all answers in detail, step by step. if it was correct I mark you as brainliest.....Quickkkkkk...

Answer 1

Hey,

1) f u = 60 cm
infinity (v) = ?
Using formula,
1/f = 1/v - 1/u
On solving,
v = -60 cm.

2) a) Since focal length is the reciprocal of the power of a lens,
f = 1 / -5.5
f = - 0.18 m.

b) f = 1 / 1.5
f = 0.67 m.

3) f = 12 cm
u = - 20 cm
Applying formula,
1/f = 1/v - 1/u
1/12 = 1/v - 1/ - 20
1/v = 2/60
v = 30 cm.

Image will be formed beyond 2F. Nature - Real, inverted and magnified.

4) v = 50 cm
ATQ,
v = u = 50 cm.
So,
The needle must be placed at a distance of 50 cm in front of the convex lens to make the size of the image equal to the size of the object.


Hope this helps you buddy!!
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Answer 2

Answer:

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