The light bulb in your room is not very bright. you want to use a concave mirror to direct its illumination into a tight, parallel beam of light for reading. the radius of curvature of the mirror is 30 centimeters. at what distance from the mirror should you place the light bulb to produce this parallel light beam

A point source is to be used with a concave mirror to produce a beam of parallel light. The source should be placed midway between the center of curvature and the mirror. To solve this question you have to draw a ray diagram. Apply the mirror equation to determine the image distance and finally make sure that the first two steps are consistent with each other.

I hope this helps, Regards.

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.