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12th Physics weekly Test -1 (Dual Nature of Radiation and Matter )

St. Britto Hr. Sec. School - Madurai

12th Physics weekly Test -1 (Dual Nature of Radiation and Matter )-Aug 2020

Time : 1.30 Hours

Part - A

Multiple Choice Question - Answer All Question

Emission of electrons by the absorption. of heat energy is called __________ emission.

photoelectric
field
thermionic
secondary

A light of wavelength 500 nm is incident on a sensitive plate of photoelectric work function 1.235 eV. The kinetic energy of the photo electrons emitted is be (Take h = 6.6 x 10^-34 Js)

0.58 eV
2.48 eV
1.24 eV
1.16 eV

Two radiations with photon energies 0.9 e V and 3.3 e V respectively are falling on a metallic surface successively. If the work function of the metal is 0.6 e V, then the ratio of maximum speeds of emitted electrons will be

1:4
1:3
1:1
1:9

In photoelectric emission, a radiation whose frequency is 4 times threshold frequency of a certain metal is incident on the metal. Then the maximum possible velocity of the emitted electron will be

\(\sqrt { \frac { { hv }_{ 0 } }{ m } } \)
\(\sqrt { \frac { { 6hv }_{ 0 } }{ m } } \)
2\(\sqrt { \frac { { hv }_{ 0 } }{ m } } \)
\(\sqrt { \frac { { hv }_{ 0 } }{ 2m } } \)

When a metallic surface is illuminated with radiation of wavelength \({ \lambda }\), the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2\({ \lambda }\), the stopping potential is \(\frac { V }{ 4 } \) . The threshold wavelength for the metallic surface is

4\({ \lambda }\)
5\({ \lambda }\)
\(\frac { 5 }{ 2 } \)\({ \lambda }\)
3\({ \lambda }\)

Photons of wavelength \(\lambda \) are incident on a metal. The most energetic electrons ejected from the metal are bent into a circular arc of radius R by a perpendicular magnetic field having magnitude B. The work function of the metal is

\(\frac { hc }{ \lambda } -{ m }_{ e }+\frac { { e }^{ 2 }{ B }^{ 2 }{ R }^{ 2 } }{ { 2m }_{ e } } \)
\(\frac { hc }{ \lambda } +{ 2m }_{ e }\left[ \frac { eBR }{ { 2m }_{ e } } \right] ^{ 2 }\)
\(\frac { hc }{ \lambda } -{ m }_{ e }{ c }^{ 2 }\frac { { e }^{ 2 }{ B }^{ 2 }{ R }^{ 2 } }{ { 2m }_{ e } } \)
\(\frac { hc }{ \lambda } -{ 2m }_{ e }\left[ \frac { eBR }{ { 2m }_{ e } } \right] ^{ 2 }\)

A particle of mass 3 x 10^-6 g has the same wavelength as an electron moving with a velocity 6 x 10⁶ms^-1. The velocity of the particle is

1.82 x 10^-18 ms^-1
9 x 10^-2 ms^-1
3 X 10^-31 ms^-1
1.82 x 10^-15 ms^-1

The wavelength \({ \lambda }_{ e }\) of an electron and \({ \lambda }_{ p }\) of a photon of same energy E are related by

\({ \lambda }_{ p }\propto { \lambda }_{ e }\)
\({ \lambda }_{ p }\propto \sqrt { { \lambda }_{ e } } \)
\({ \lambda }_{ p }\propto \frac { 1 }{ \sqrt { { \lambda }_{ e } } } \)
\({ \lambda }_{ p }\propto { { \lambda } }_{ e }^{ 2 }\)

If a light of wavelength 330 nm is Incident on a metal with work function 3.55 eV, the electrons are emitted. Then the wavelength of the emitted electron is (Take h = 6.6 x 10^-34 Js)

< 2.75 x 10^-9m
\(\ge \) 2.75x10^-9m
\(\ge \)2.75x10^-12m
< 2.5 x 10^-10m

A photoelectric surface is illuminated successively by monochromatic light of wavelength \(\lambda \) and \(\frac { \lambda }{ 2 } \)If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function at the surface of material is

\(\frac { hc }{ \lambda } \)
\(\frac { 2hc }{ \lambda } \)
\(\frac { hc }{ 3\lambda } \)
\(\frac { hc }{ 2\lambda } \)

The mean wavelength of light from sun is taken to be 550 nm and its mean power is 3.8 x 10²⁶W. The number of photons received by the human eye per second on the· average from sunlight is of the order of

10⁴⁵
10⁴²
10⁵⁴
10⁵¹

In an electron microscope, the electrons are accelerated.by a voltage of 14 kV. If the voltage is changed to 224 kV, then the de Broglie wavelength associated with the electrons would

increase by 2 times
decrease by 2 times
decrease by 4 times
increase by 4 times

The work functions for metals A, Band Care 1.92 eV, 2.0 eV and 5.0 eV respectively. The metals which will emit photoelectrons for a radiation of wavelength 4100 \(\mathring { A } \) is/are

A only
both A and B
all these metals
none

The threshold wavelength for a metal surface whose photoelectric work function is 3.313 eV is

4125 \(\mathring { A } \)
3750 \(\mathring { A } \)
6000 \(\mathring { A } \)
2062.5 \(\mathring { A } \)

A light source of wavelength 520 nm emits 1.04 x 10¹⁵ photons per second while the second source of 460 nm produces 1.38 x 10¹⁵ photons per second. Then the ratio of power of second source to that of first source is

1.00
1.02
1.5
0.98

Part - B

Generic 2 - Answer All Question

What is a photo cell? Mention the different types of photocells.

Write the expression for the de Broglie wavelength associated with a charged particle of charge q and mass m, when it is accelerated through a potential V.
Give the definition of intensity of light and its unit.

How does photocurrent vary with the intensity of the incident light?

A proton and an electron have same kinetic energy. Which one has greater de Broglie wavelength. Justify.

State de Broglie hypothesis.

Part - C

Generic 5 - Answer All Question

An electron is accelerated through a potential difference of 81V. What is the de Broglie wavelength associated with it? To which part of electromagnetic spectrum does this wavelength correspond?

How many photons per second emanate from a 50 m W laser of 640 nm?

A deuteron and an alpha particle are, accelerated with the same potential. Which one of the two has i) greater value of de Broglie wavelength associated with it and ii) less kinetic energy? Explain
When a light of frequency 9 x10¹⁴ Hz .is incident on a metal surface, photoelectrons are emitted with a maximum speed of 8 x 10⁵ms^-1. Determine the threshold frequency of the surface.

Derive an expression for de Broglie wavelength of electrons.

Calculate the de Broglie wavelength of a proton whose kinetic energy is equal to 81.9 x 10^-15 J. (Given: mass of proton is 1836 times that of electron).

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