The speed of an electron having a wavelength of 10^-10 m is

• 7.25 × 10⁶ m/s

• 5.25 × 10⁶ m/s

• 6.26 × 10⁶ m/s

• 4.24 × 10⁶ m/s

Colour of star depends upon

• luminosity

• temperature

• brightness

• all of these

The work function of a metal is 3.4 eV. If the frequency of incident radiation is increased to twice, then the work function of the metal becomes

• 3.4 eV

• 7.2 eV

• 6.8 eV

• 1.7 eV

If red light is replaced by white light then width of diffraction pattern will

• increases

• decreases

• a central white band is obtained

• no effect

In Planck's oscillator energy is given as

     E = $\frac{\mathrm{h\nu }}{\exp \left({\displaystyle \frac{\mathrm{h\nu }}{\mathrm{Kt}}} - 1 \right)}$  If K = 0, then energy would be

• hν

• 0

• Kt

• ∞

Assertion: On increasing the frequency of light larger number of photoelectrons are emitted. 

Reason:  The number of electrons emitted depends on the intensity of incident light.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reasonn are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If assertion is false but reason is true.

Maximum velocity of photoelectron emitted is 4.8m/s. If e/m ratio of the electron is $1.76 \times {10}^{11} {\mathrm{CKg}}^{-1}$ then stopping potential is given by

• 5 $\times$ 10^-10 J/C

• 3 $\times$ 10^-7 J/C

• 7 $\times$ 10^-11 J/C

• 2.5 $\times$ 10^-2 J/C

The de-Broglie wavelength of an electron having 80 eV of energy is nearly (1 eV = 1.6 × 10^-19J, mass of electron = 9.1 × 10^-31 kg, Planck's constant = 6.6 × 10^-34 J-s)

• 140 Å

• 0.14 Å

• 14 Å

• 1.4 Å

When light of wavelength 300 nm falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, light of wavelength 600 nm is sufficient for liberating photoelectrons. The ratio of the work function of the two emitters is

• 1 : 2

• 2 : 1

• 4: 1

• 1: 4

Maximum velocity of the photoelectrons emitted by a metal surface is 1.2x10⁶ ms^-1. Assuming the specific charge of the electron to be 1.8 x10¹¹ C kg^-1, the value of the stopping potential in volt will be

• 2

• 3

• 4

• 6