Question

An object 6cm in size is placed 20cm in front of a concave mirror of focal length 12 CM. At what distance should a screen be placed from the mirror in order to obtain sharp image? Find the nature and size of the image

Answer 1

Answer: Now here in this question we have given some values,

V=?, u= -20cm, f= -12cm... (1)

Now mirror formulae

, 1/v+1/u=1/f...(2)

Now use 1 in 2

1/v+1/-20=1/-12

1/v=1/-12+1/20

Now by taking LCM in RHS

We get, 1/v=-5+3/60

1/v=-2/60

Then, v=-2/60=-30cm.

Nature of image = real and inverted.

Now first we find our h and then size of image,

m=h'/h=v/-(-u)

m=6/h=-30/+20

Then h= -4cm

Now use this value, for finding m

Such as m=h'/h

, m=6/-4= -1.5cm

Explanation:

Answer 2

1. Answer: Now here in this question we have given some values,
3. Explanation:
5. V=?, u= -20cm, f= -12cm... (1)
7. Now mirror formulae
9. , 1/v+1/u=1/f...(2)
11. Now use 1 in 2
13. 1/v+1/-20=1/-12
15. 1/v=1/-12+1/20
17. Now by taking LCM in RHS
19. We get, 1/v=-5+3/60
21. 1/v=-2/60
23. Then, v=-2/60=-30cm.
25. Nature of image = real and inverted.
27. Now first we find our h and then size of image,
29. m=h'/h=v/-(-u)
31. m=6/h=-30/+20
33. Then h= -4cm
35. Now use this value, for finding m
37. Such as m=h'/h
39. , m=6/-4= -1.5cm