Question
A magnifying glass held 25 cm from a desk lamp projects a focused image on a wall 1.6 m from the lamp. Determine the focal length of the magnifying glass? Two harmonic waves traveling in opposite directions interface to produce a standing wave described by y = 2sin(pi x)cos(3 pi) where x is in meters and t is in s. What is the distance (in m) between the first two antinodes? 8 2 4 1 0.5 Bonus: A 3.00 mW laser pointer makes a 1.00 mm beam spot on a projection screen. Determine the radiation pressure on a screen that reflects 50.0 % of the light incident on it.
Explanation / Answer
9.
do = object distance = 25 cm
di = image distance from glass = 160 - 25 = 135 cm
using lens equation
1/f = 1/di + 1/do
1/f = 1/135 + 1/25
f = 21.1 cm