Question 32
Light and ReflectionAn object is placed 5cm from the pole of a concave mirror. If the focal length of the mirror is 10 cm, what is the image distance?
- A.10 cm in front of the mirror
- B.5 cm in front of the mirror
- C.10 cm behind the mirror
- D.5 cm behind the mirror
Show the answer and explanation
Answer: C (10 cm behind the mirror)
Explanation
1/v = 1/f − 1/u = 1/10 − 1/5 = −1/10, so v = −10 cm. The negative sign means a virtual image 10 cm behind the mirror.