 #1
 427
 2
# A convergent beam is incident on a concave lens as shown in figure. Which of the following is not correct?
a) The image formed is real
b) The image formed is virtual
c) The image formed is erect
d) The image formed is magnified
I solved it in the following way:
Let f be the focal length of the concave lens and let v be the image distance. From the figure, object distance = f(virtual object), Focal length = f(focal length of concave lens is negative)
(1/ object distance) + (1/image distance) = 1/ Focal length
(1/f) + (1/v) = 1/f
Solving I get,
v = + infinity
Magnification = v/u = ( infinity)/(f)
= + infinity
Since Magnification is positive the image is erect. Since the Magnification is infinity the image is magnified. Since the image distance is positive the image is real. So the answer is (b). Is my argument right?
a) The image formed is real
b) The image formed is virtual
c) The image formed is erect
d) The image formed is magnified
I solved it in the following way:
Let f be the focal length of the concave lens and let v be the image distance. From the figure, object distance = f(virtual object), Focal length = f(focal length of concave lens is negative)
(1/ object distance) + (1/image distance) = 1/ Focal length
(1/f) + (1/v) = 1/f
Solving I get,
v = + infinity
Magnification = v/u = ( infinity)/(f)
= + infinity
Since Magnification is positive the image is erect. Since the Magnification is infinity the image is magnified. Since the image distance is positive the image is real. So the answer is (b). Is my argument right?
Attachments

1.5 KB Views: 483