Which one of the following electromagnetic radiations have the smallest wavelength?
X-rays
y-rays
Ultraviolet waves
Microwaves
The velocity of electromagnetic wave is along the direction of
Which of the following has minimum wavelength?
Ultraviolet rays
Cosmic rays
A TV tower has a height of 100 m. How much population is covered by the TV broadcast if the average population density around the tower is 1000 km-2 (radius of earth = 6370 km)?
4 lakh
40,000
4000
40 lakh
Electromagnetic waves are
transverse waves
longitudinal waves
produced by charges moving with constant velocity
none of the above
If λv, λx and λm represent the wavelengths of visible light, X-rays and microwaves respectively, then
λm > λx > λv
λv > λm > λx
λm > λv > λx
λv > λx > λm
The charging current for a capacitor at any instant is 0.25 A.The displacement current across the capacitor plates at that instant is
0.5 A
0.25 A
2.5 A
1 A
A signal emitted by an antenna from a certain point can be received at another point of the surface in the form of
cosmic rays
sky wave
sea wave
both (a) and (b)
In a plane electromagnetic wave, the electric field oscillates with a frequency of 2 × 1010 s-1 and an amplitude of 40 Vm-1. The wavelength of the wave is
3 × 10-3 m
2.5 × 10-2 m
1.5 × 10-2 m
4.5 × 10-3 m
What is the cause of "Green house effect"?
Infrared rays
Radio-waves