Hold a concave mirror in your hand and direct its reflecting surface towards the sun. Direct the light…
Hold a concave mirror in your hand and direct its reflecting surface towards the sun. Direct the light reflected by the mirror on to a white card-board held close to the mirror. Move the card-board back and forth gradually until you find a bright, sharp spot of light on the board. This spot of light is the image of the sun on the sheet of paper; which is also termed as "Principal Focus" of the concave mirror.
(a) List two applications of concave mirror.
(b) If the distance between the mirror and the principal focus is 15 cm, find the radius of curvature of the mirror.
(c) Draw a ray diagram to show the type of image formed when an object is placed between pole and focus of a concave mirror.
Solution
(a) Torches, search light, vehicles head lights, shaving mirrors, dentist's mirror, Solar furnaces. (any two)
(b) f = 15cm
R = 2f
R = 2 × 15 cm = 30 cm
(c) [Ray diagram: concave mirror with object AB placed between C and F, image A'B' formed]
(Note: ½ mark to be deducted for not drawing the arrows.)
