Question

Light from a distant star is collected by a concave mirror that has a radius of curvature of 150 cm. How far from the mirror is the image of the star?

Answer 1

The focal point of a mirror is half of the radius of curvature. We can use the formula,                                                                                                                   1/f = 1/v + 1/u                                                                                                          where f is the focal length , v is the image distance and u is object distance        The distance of the star is assumed to be incredibly far away and 1 divided by a really big number is approximately zero, thus;                                                     1/f = 1/v  = 1/75 = 1/v                                                                                             therefore; the image is formed 75 cm infront of the mirror