Question

a pin of length 2 cm is placed perpendicular to the principal Axis at a distance of 20 cm from a concave mirror whose focal length is 10 cm. where should a screen be placed to get the image on it. also calculate the length of image​

Answer 1

according to me distance of image is -20 and height of image is -4 . the negative sign come from sign convention.

solution:-

. we know that 1/f = 1/u + 1/v

then we have

ho=2cm , u =20cm , f=10cm

then 1/-10 =1/-20 + 1/v

1/-10 +1/20 =1/v

-2+1/20=1/v

-1/20=1/v

-20=v ans. 1

we also know that m=hi/ho =-v/u

hi/2=-(-20)/-10

hi/2=-2

hi=-4 ans. 2

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