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When an electron accelerated by potential difference $U$ is bombarded on a specific metal, the emitted $X -$ ray spectrum obtained is shown in adjoining graph. If the potential difference is reduced to $\frac{U}{3},$ the correct spectrum is

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Important Questions on Modern Physics - I

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#1>Q 14

In the hydrogen atom, an electron makes a transition from

n = 2

n = 1 .

The magnetic field produced by the circulating electron at the nucleus

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#1>Q 15

An electron in a hydrogen atom makes a transition from first excited state to ground state. The equivalent current due to circulating electron

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#1>Q 16

An orbital electron in the ground state of hydrogen has an angular momentum

L_{1}

and an orbital electron in the first orbit in the ground state of lithium (double ionised positively charged) has an angular momentum

L_{2} .

Then

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#1>Q 17

If in the first orbit of a hydrogen atom the total energy of the electron is

- 21.76 \times 10^{- 19} J,

then its electric potential energy will be:

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#1>Q 18

In the photoelectric experiment, if we use a monochromatic light, the $I - V$ curve is as shown. If work function of the metal is $2 eV,$ estimate the power of light used. (Assume efficiency of photo emission is $10^{- 3} %,$ i.e. number of photoelectrons emitted are $10^{- 3} %$ of number of photons incident on metal.)

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#1>Q 19

The work function of a certain metal is

\frac{h C}{λ_{0}}

when a monochromatic light of wavelength,

λ < λ_{0}

is incident such that the plate gains a total power

P

. If the efficiency of photoelectric emission is

η %

and all the emitted photoelectrons are captured by a hollow conducting sphere of radius

R

already charged to potential

V

, then, neglecting any interaction between plate and the sphere, expression of potential of the sphere at time

t

is,

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#1>Q 20

A monochromatic beam of electromagnetic radiation has an intensity of

1 W m^{- 2}

. Then the average number of photons per

m^{3}

for a

10 MeV

γ

rays is

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#1>Q 21

When light of intensity

1 W m^{- 2}

and wavelength

5 \times 10^{- 7} m

is incident on a surface, it is completely absorbed by the surface. If

100

photons emit one electron and area of the surface is

1 {cm}^{2},

then the photoelectric current will be

When an electron accelerated by potential difference U is bombarded on a specific metal, the emitted X-ray spectrum obtained is shown in adjoining graph. If the potential difference is reduced to U3, the correct spectrum is

Important Questions on Modern Physics - I

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When an electron accelerated by potential difference $U$ is bombarded on a specific metal, the emitted $X -$ ray spectrum obtained is shown in adjoining graph. If the potential difference is reduced to $\frac{U}{3},$ the correct spectrum is