Optics Question 927
Question: A concave mirror gives an image three times as large as the object placed at a distance of $ 20cm $ from it. For the image to be real, the focal length should be
[SCRA 1998; JIPMER 2000]
Options:
A) $ 10cm $
B) $ 15cm $
C) $ 20cm $
D) $ 30cm $
Show Answer
Answer:
Correct Answer: B
Solution:
$ m=\frac{f}{f-u} $
$ \Rightarrow -\ 3=\frac{f}{f-(-20)} $
$ \Rightarrow f=-15cm $
