A lamp emits monochromatic green light uniformly in all directions. The lamp is 3% efficient in converting electrical power to electromagnetic waves and consumes 100 W of power. The amplitude of the electric field associated with the electromagnetic radiation at a distance of 5 m from the lamp will be nearly
a.1.34 V/m
b.2.68 V/m
c.4.02 V/m
d.5.36 V/m
A toy - car, blowing its horn, is moving with a steady speed of 5 m/s, away from a wall. An observer, towards whom the toy car is moving, is able to hear 5 beats per second. If the velocity of sound in air is 340 m/s, the frequency of the horn of the toy car is close to:
a.680 Hz
b.510 Hz
c.340 Hz
d.170 Hz
An observer looks at a distant tree of height 10 m with a telescope of magnifying power of 20 . To the observer the tree appears:
a.10 times taller
b.10 times nearer
c.20 times taller
d.20 times nearer
A tuned amplifier circuit is used to generate a carrier frequency of 2 MHz for the amplitude modulation. The value of (LC) is
a.12pi x 10^6
b.12 x 10^6
c.13pi x 10^6
d.14pi x 10^6
Two points on a travelling wave having frequency 500 Hz and velocity 300m/s are 60^o out of phase, then the minimum distance between the two points is
a.0.2
b.0.1
c.0.5
d.0.4