A photo cell with a constant potential difference of V volts applied across its ends is illuminated by a point source from a distance of 25 cm. If the source is moved to a distance of 1 m, then electrons emitted from the photo cell will be

1.carry 1 / 4 th of their previous energy

2.are 1 / 6 th as numerous as before

3.are - 1 / 16 th as numerous as before

4.carry 1 / 4 th of their previous momentum

**Posted Date**:-2021-09-26 06:35:31

A proton is accelerated through one volt. The increase in it K.E. is approximately

1.1870 eV

2.1 eV

3.300 eV

4.None of these

**Posted Date**:-2021-09-26 06:35:31

At stopping potential

1.K.E. = 0

2.P.E. = 0

3.K.E. = P.E

4.K.E. + P.E. = 0

**Posted Date**:-2021-09-26 06:35:31

Charge on a stationary oil drop in Millikan s experiment is ne. Potential difference between the plates is 400 volts. If mass of the drop is doubled without changing the charge, then potential drop required to keep the drop stationary is

1.200 volts

2.800 volts

3.1600 volts

4.3200 volts

**Posted Date**:-2021-09-26 06:35:31

If frequency of the wave emitted from a radio stations is 6 MHz. Then wavelength of waves will be

1. 12 m

2.24 m

3.50 m

4.6 m

**Posted Date**:-2021-09-26 06:35:31

If photons of 60 nm are incident on hydrogen then max KE of the emitted electrons will be

1.5.0 eV

2.6.3 eV 6.3 eV

3.7.0 eV

4.7.9 eV

**Posted Date**:-2021-09-26 06:35:31

If the momentum of a particle is doubled, then wavelength associated with particle will be

1.remains unchanged

2.half

3.double

4.None of these

**Posted Date**:-2021-09-26 06:35:31

If wavelength of an electron and a photon is same, then they will have same

1.Velocity

2.Momentum

3.Energy

4.All of above

**Posted Date**:-2021-09-26 06:35:31

In Einstein s photoelectric equation E = hv - W where E stands for

1.K.E. of emitted electrons

2.Maximum P.E. of emitted electrons

3.Mean kinetic energy of the incident particles

4.Total energy of all the emitted electrons

**Posted Date**:-2021-09-26 06:35:31

It kinetic energy of the emitted electted electrons is zero for the incident light of wavelength 686 nm. Then wavelength of radiations emitting electrons having energy 1.81 eV will be (Given : work function of cesium = 1.81 eV)

1.686 nm

2.1372 nm

3.343 nm

4.2058 nm

**Posted Date**:-2021-09-26 06:35:31

Photon A has twice the wavelength of photon B then energy of photon A is

1.Half that of B

2.Twice that of B

3.Thrice that of B

4.Four times that of B

**Posted Date**:-2021-09-26 06:35:31

Photons of energy 5.0 eV fall on a metal surface whose work function is 2.0 eV. Then

1.most energetic electron will have kinetic energy equal to 5.0 eV

2.all photoelectrons will have same energy of 2.0 eV

3.kinetic energy of most energetic electron will be 2.0 eV

4.kinetic energy of most energetic electron will be 3.0 eV

**Posted Date**:-2021-09-26 06:35:31

Rest mass energy of an electron is 0.54 MeV. If velocity of the electron is 0.8 C then K.E. of the electron is

1.0.36 MeV

2.0.41 MeV

3.0.48 MeV

4.1.32 MeV

**Posted Date**:-2021-09-26 06:35:31

Rest mass of a photo is

1.9.31 eV

2.13.6 eV

3.2.6 eV

4.zero

**Posted Date**:-2021-09-26 06:35:31

Rest mass of an electron is 051 MeV If it is given a velocity of 08 c its kinetic energy will be

1.0.27 MeV

2.0.34 MeV

3.0.68 MeV

4.0.68 MeV

**Posted Date**:-2021-09-26 06:35:31

Three particles having their charges in the ratio of 1 : 3 : 5 produce the same spot on the screen in Thomson experiment. Their masses are in the ratio of

1.5:03:01

2.3:01:05

3.1:03:05

4. 5 : 1 : 3

**Posted Date**:-2021-09-26 06:35:31

When a monochromatic point source of light is at a distance of 0.2 m from a photoelectric cell cut off voltage and the saturation current are respectively 0.6 V and 18.0 mA. If same source is placed 0.6 m away from the photoelectron cell then

1.saturation current will be 1 / 4 th of their previous value

2.saturation current will be 18 mA

3.stopping potential will be 0.6 V

4.saturation current will be 6 mA

**Posted Date**:-2021-09-26 06:35:31

When a monochromatic point source of light is at a distance of 0.2 m from photoelectric cell, the cut-off voltage and the saturation current are 0.6 V and 18.0 mA respectively. If the same source is placed 0.6 m away from the photo cell, then

1.the stopping potential will be 0.2 V

2.the stopping potential will be 0.6 V

3.the saturation current will be 2.0 mA

4.the saturation current will be 6.0 mA

**Posted Date**:-2021-09-26 06:35:31

When distance between a monochromatic source and photo cell is 20 cm then cut off voltage and saturation currents are 0.6 volt and 18.0 mA respectively . If distance between the two is increased to 60 cm then

1.saturation current will be 2.0 mA

2.saturation current will be 6.0 mA

3.stopping potential will be 0.2 volt

4.stopping potential will be 0.6 volt

**Posted Date**:-2021-09-26 06:35:31

Work function of aluminium is 4.2 eV. If two photons each of energy 3.5 eV strike an electron of aluminum, then emission of electron

1.will be possible

2.depends on the smoothness of the surface

3.will not be possible

4.None of these

**Posted Date**:-2021-09-26 06:35:31

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