Two diverging light rays, originating from the same point, have an angle of 5° between them. After the rays reflect from a plane
mirror, what is the angle between them? Construct one possible ray diagram that supports your answer.
2 answers:
Answer:
5°
Explanation:
Two diverging light rays, originating from the same point, have an angle of 5° between them.
According to laws of reflection the angle of incidence is equal to the angle of reflection.
From the attached figure, it is clear that the after reflection from a plane mirror the angle between two rays will be 5°.
O be the originating point. m and n two diverging light rays. When they strikes at the plane mirror, the laws of reflection still fulfilled.
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(a) -83.6 Hz
Due to the Doppler effect, the frequency of the sound of the train horn appears shifted to the observer at rest, according to the formula:
where
f' is the apparent frequency
v = 343 m/s is the speed of sound
is the velocity of the source of the sound (positive if the source is moving away from the observer, negative if it is moving towards the observer)
f is the original frequency of the sound
Here we have
f = 350 Hz
When the train is approaching, we have
So the frequency heard by the observer on the platform is
When the train has passed the platform, we have
So the frequency heard by the observer on the platform is
Therefore the overall shift in frequency is
And the negative sign means the frequency has decreased.
(b) 0.865 m
The wavelength and the frequency of a wave are related by the equation
where
v is the speed of the wave
is the wavelength
f is the frequency
When the train is approaching the platform, we have
v = 343 m/s (speed of sound)
f = f' = 396.7 Hz (apparent frequency)
Therefore the wavelength detected by a person on the platform is