An object is placed 36cm from a converging lens of focal length 24cm.If a real image which is 4cm high is formed, Calculate the height of the object.
A
2.0cm
B
4.0cm
C
6.0cm
D
8.0cm
E
10.0cm
Verified Correct Answer: A.
Physical Principles & Numerical Solution
F = 24cm , U = -36cm(behind lense)
Applying Lense formula = \(\frac {1}{f} = \frac{1}{v} - \frac{1}{u}\)
\(\frac{1}{v} = \frac{1}{24} - \frac{1}{36} = \frac{1}{72}\)
v = 72cm
but Magnification = \(\frac{V}{U} = \frac{h^i}{h_o}\)
\(\frac{72}{-36} = \frac{-4}{h_o}\) \( h_1\) = -4( real image is negative)
by cross multiplying \(h_1\) = 2cm
Source: Myschool Past Questions Archive (Record #21242)