infrared radiations are used in security alarms. in these kind of security alarms , when a beam of infrared radiation is blocked by an intruder, it triggers the security alarms for a fixed amount of time.it is used because it is invisible and can not be detected by an intruder. warm objects emits infrared radiation. this fact is used to detect in dark.
Answer:
39267.96 Hz
Explanation:
Given:
Frequency emitted = 16246 Hz
Speed of source = 141 m/s
Speed of observer = 141 m/s
Let the velocity of sound is v = 340 m/s
Doppler effect is nothing but the change in the wavelength or frequency of a wave relative to the observer, who is also moving relative to the origin of the wave source.
Therefore, Doppler effect when the source and the observer moves towards each other,
Frequency heard = ( frequency emitted ) ( Velocity of sound + Speed of the observer ) / ( velocity of sound - speed of source )
16246 x ( 340 + 141 ) / ( 340 - 141 )
= 39267.96 Hz
Answer:
v/c = 0.76
Explanation:
Formula for Length contraction is given by;
L = L_o(√(1 - (v²/c²))
Where;
L is the length of the object at a moving speed v
L_o is the length of the object at rest
v is the speed of the object
c is speed of light
Now, we are given; L = 65%L_o = 0.65L_o, since L_o is the length at rest.
Thus;
0.65L_o = L_o[√(1 - (v²/c²))]
Dividing both sides by L_o gives;
0.65 = √(1 - (v²/c²))
Squaring both sides, we have;
0.65² = (1 - (v²/c²))
v²/c² = 1 - 0.65²
v²/c² = 0.5775
Taking square root of both sides gives;
v/c = 0.76
Answer:
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