an object of height 7cm is kept at a distance of 25cm in front of a concave mirror . the focal length of the mirror is 15 cm .at what distance from the mirror should a screen be kept so as to get a clear image ? what will be the size and nature ofthe image ?
Answers
where
object distance (u)=−25cm
image distance (v)=?
focal length(f)=−15cm
(for concave mirror)
Inserting these values we get
1v−125=−115
⇒1v=125−115=3−575=−275
v=−37.5
So real image (as represented by -ve image dist.) will be formed at distance 37.5cm
Answer:
given : height of object= 7cm
object distance= -25cm
focal length = -15cm
image distance = ?
height of image = ?
1. as the image is to be obtained on a screen, it must be real.
2. 1/v + 1/u =1/f
therefore 1/v = 1/f - 1/u = 1/-15cm - 1/-25cm
=-(1/15cm -1/25cm)
= -(5-3)/75cm = -2/75cm
therefore v = -74cm /2 = -37.5cm
this gives the image distance. therefore, the screen should be placed in front of the mirror at 37.5cm from it.
3. h2/h1= -v/u
therefore, = h2 = - h1 v/u
therefore, h2= -7cm×(-37.5 cm)/(-24cm)
=-7×1.5cm
= -10.5 cm
the size of the image, h2 = -10.5 cm
the minus sign shows that the image is inverted
Explanation:
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