Answer: The frequency heard will be f = 275.675Hz
Explanation: When an object emitting sound is moving, it occurs a phenomenon called Doppler shift or Doppler effect. What happens is that the sound gets higher when the moving object comes closer the observer and becomes lower after it passes, This change is due to the quantity of waves that passes through an area in an unit of time.
The formula to calculate the Doppler effect is as follows
f = (
) · f₀
f is the observed frequency;
c is the speed of sound;
Vs is velocity of the source;
f₀ is the emitted frequency of source;
Substituting and calculating,
f = 
· 300
f = 275.675 Hz
Thus, the frequency heard by the police officer is 275.675Hz.
A) To obtain an inverted image of an object of same size a convex lens is used.
B)
In this question we have given
Distance between candle flame and screen=4
it means distance between candle flame and lens +distance between lens and screen =4m
u+v= 4m
u= v
therefore, 2u= 4m
or, u=-2m ( u is taken negative because it lies on left side of the lens)
and v=2m
we have to find the focal length of convex lens
Hence, Focal length of the lens is 1m
and lens should be placed at a distance of 2m from the flame
(4) Elevations:
Point A: 900 ft
Point B: 900 ft
Point C: 1500 ft
Point D: 1000 ft
(5) Contour interval: 100 ft
(6) Plot #1 best fits the profile seen in the contour map.
The answer is C sorry if it’s wrong
What is happening to this sound is that it’s vibrating over and over.
