CBSE
Electrons with de-Broglie wavelength λ fall on the target in an X-ray tube. The cut-off wavelength of the emitted X-rays is
The energy of gamma (γ) ray photon is Eγ and that of an X-ray photon is Ex. If the visible light photon has an energy of Ev, then we can say that
EX > Eγ > Ev
Eγ > Ev > EX
Eγ > EX > Ev
EX > Ev > Eγ
The condition under which a microwave oven heats up a food item containing water molecules most efficiently is
the frequency of the microwave must match the resonant frequency of the water molecules
the frequency of the microwave has no relation with natural frequency of water molecules
microwave are heat waves, so always produce heating
infrared waves produce heating in a microwave oven
In which of the following phenomena, the heat waves travel along straight lines with the speed of light ?
Thermal conduction
Forced convection
Natural convection
Thermal radiation
The electric field associated with an electromagnetic wave in vaccum is given by E = i 40 cos (kz − 6 x 108 t), where E, Z and t are in volt m-1, metre and second respectively. The value of wave vector (k) is
2 m-1
0.5 m-1
6 m-1
3 m-1
Two elements A and B with atomic numbers ZA and ZB are used to produce characteristic X-rays with frequencies vA and vB respectively. If ZA : ZB = 1 : 2, then vA : vB will be
1 : 8
4 : 1
1 : 4
Which of the following electromagnetic waves have the smallest wavelength ?
γ-rays
X-rays
UV waves
infrared rays