Question

A concave mirror is placed on a horizontal table, with its axis directed vertically upwards. Let O be the pole of the mirror and C it's centre of curvature. A point object is placed at C. It has a real image, also located at C (a condition called auto-collimation). If the mirror is now filled with water, the image will be:

• A. real, and will remain at C
• B. real, and located at a point between C and $\infty$
• C. virtual, and located at a point between C and O
• D. real, and located at a point between C and O

Answer 1

Answer: (D)

Due to refraction at water surface object will appear beyond C. This image will act as an object for reflection by mirror. So image will be real, and located between C and O