EASY

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How is photoelectric current affected on increasing frequency?

Important Questions on Photoelectric Emission and Production and Properties of X-rays

HARD

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

In a photoelectric experiment, a parallel beam of monochromatic light with the power of

200 W

is incident on a perfectly absorbing cathode of work function

6.25 eV

. The frequency of light is just above the threshold frequency so that the photoelectrons are emitted with negligible kinetic energy. Assume that the photoelectron emission efficiency is 100%. A potential difference of

500 V

is applied between the cathode and the anode. All the emitted electrons are incident normally on the anode and are absorbed. The anode experiences a force

F = n \times 10^{- 4} N

due to the impact of the electrons. The value of

n

is __________. Mass of the electron

m_{e} = 9 \times 10^{- 31} kg a n d 1.0 eV = 1.6 \times 10^{- 19} J

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

The anode voltage of a photocell is kept fixed. The wavelength

λ

of the light falling on the cathode is gradually changed. The plate current

I

of the photocell varies as follows :

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

Radiation of wavelength

300 nm

and intensity

100 W m^{- 2}

falls on the surface of a photosensitive material. If

2 %

of the incident photons produce photo electron, the number of photoelectrons emitted from an area of

2 {cm}^{2}

of the surface is nearly

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

Draw graphs showing variation of photoelectric current with applied voltage for two incident radiations of equal frequency and different intensities. Mark the graph for the radiation of higher intensity.

EASY

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

A point source of light is used in an experiment of photoelectric effects. If the distance between the source and the photoelectric surface is doubled, which of the following may result?

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

As the intensity of incident light increases

EASY

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

In a photoelectic experiment the incident photons have frequency

\frac{3}{2} v,

where

v

is the threshold frequency. The stopping potential is

V .

If the frequency of the incident photons is changed to

\frac{3}{4} v,

then the correct statement is

EASY

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

With reference to photoelectric effect, define threshold wavelength.

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

The work function of copper is

4.7 eV

. If ultraviolet light of wavelength

312 nm

and intensity

1.0 W m^{- 2}

is directed on a copper plate, then in the detector

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

The work function of three photosensitive materials used to build photoelectric devices are given as : Sodium $(2.75 eV),$ copper $(4.65 eV)$ and gold $(5.1 eV) .$ Which of the following statements is correct. (The frequency of visible light lies in the range $4 \times 10^{14} Hz$ to $8 \times 10^{14} Hz) ?$

EASY

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

Draw a graph showing variation of photocurrent with the anode potential of a photocell.

EASY

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

When a beam of

10.6 eV

photons of intensity

2.0 W m^{- 2}

falls on a metallic surface of area

1 \times 10^{- 4} m^{2}, 0.53 %

of the incident photons eject photoelectrons. What is the number of photoelectrons emitted per second?

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

The variation of the stopping potential $(V_{\circ})$ with the frequency $(ν)$ of the light incident on two different photosensitive surfaces M1 and M2 is shown in the figure. Identify the surface which has greater value of the work function.

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EASY

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

The work function of a metal is

h v_{0}

. Light of frequency

v

falls on this metal. The photoelectric effect will take place only if

EASY

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

In Lenard's experiment, the maximum value of photoelectric current is called _____.

EASY

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

Define the following with reference to photoelectric effect $:$

$(a)$ Threshold frequency $(f_{o})$

EASY

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

Green light ejects electron from a certain photo-sensitive surface, but yellow light does not. What will happen in case of red and violet light?

MEDIUM

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

A certain metallic surface is illuminated by monochromatic radiation of wavelength

λ

. The stopping potential for photoelectric current for this radiation is

3 V_{0} .

If the same surface is illuminated with a radiation of wavelength

2 λ,

the stopping potential is

V_{0} .

The threshold wavelength of this surface for photoelectric effect is____

λ .

HARD

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

A zinc ball of radius,

R = 1 cm

charged to a potential

- 0.5 V .

The ball is illuminated by a monochromatic ultraviolet

(U V)

light with a wavelength

290 nm .

The photoelectric threshold for zinc is

332 nm .

The potential of ball after a prolonged exposure to the

U V

EASY

Physics>Modern Physics>Photoelectric Emission and Production and Properties of X-rays>Photoelectric Effect

When a certain photosensitive surface is illuminated with a monochromatic light of frequency

ν,

the stopping potential of the photo current is

- \frac{V_{0}}{2} .

When the surface is illuminated by monochromatic light of frequency

\frac{ν}{2},

the stopping potential is

- V_{0} .

The threshold frequency for photoelectric emission is

How is photoelectric current affected on increasing frequency?

Important Questions on Photoelectric Emission and Production and Properties of X-rays

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