A real object is 30 cm from a negative lens that has a focal length f = -20 cm.The image is
A)virtual and 30 cm from the lens.
B)real and 12 cm from the lens.
C)virtual and 12 cm from the lens.
D)real and 20 cm from the lens.
E)None of these is correct.

Question

Quizplus · Accepted Answer

According to the lens formula,
1/f = 1/di - 1/do
where f = -20 cm (focal length of the lens),
do = 30 cm (object distance from the lens),
and di is the image distance from the lens.

Substituting the given values in the formula, we get
1/-20 = 1/di - 1/30
Solving this equation, we get
di = -12 cm

The negative value of the image distance indicates that the image is virtual, which means it is formed on the same side of the lens as the object.

Therefore, the answer is (C) virtual and 12 cm from the lens.

A Real Object Is 30 Cm from a Negative Lens