2. The drawing shows a laser beam shining on a plane mirror that is perpendicula
ID: 1508068 • Letter: 2
Question
2. The drawing shows a laser beam shining on a plane mirror that is perpendicular to the floor. The beam's angle of incident is 37.9°. The beam emerges from the laser at a point that is 1.10 m from the mirror and 1.80 m above the floor. After the reflection, how far from the base of the mirror does the beam strike the floor?
3.Two plane mirrors are facing each other. They are parallel, 4 cm apart, and 16 cm in length, as the drawing indicates. A laser beam is directed at the top mirror from the left edge of the bottom mirror. What is the smallest angle of incidence with respect to the top mirror, such that the laser beam hits the mirrors in each way? (a) hits only one of the mirrors
°
(b) hits each mirror only once
°
Explanation / Answer
1-
Assuming the angle of incidence is the angle the ray forms with a line normal to the mirror at the point of incidence, the mirror planes and the ray as it travels from one mirror to the other will form a triangle with angles of (90-58), 120, and (180-120-(90-58)). Since the angle of incidence with the normal line equals the angle of reflection, the sum of angles forming a right angle is 90, and the sum of angles in a triangle is 180. Using these same three laws you can then figure out that theta2 is 62 degrees.
180-90-28= 62°
2-
tg( 90-)= d/x
x= d/tg( 90-v)
x= 0.8563 m
from the laws of reflections the angle of incidence is equal to the angle of reflection. Thus if h is the distance where the light ray strikes from the base of the mirrow then
h/(H-x)= tg(90-)
h= (H-x)*tg(90-)
h= 1.212 m
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