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The quantum hall resistance $R_{H}$ is a fundamental constant with the dimensions of resistance. If $h$ is Planck's constant and $e$ is the electronic charge, then the dimension of $R_{H}$ is the same as,

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Important Questions on Modern Physics - I

HARD

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#2>Q 11

In one model of the electron, the electron of mass

m_{e}

is thought to be a uniformly charged shell of radius

R

and total charge

e

whose electrostatic energy

E

is equivalent to its mass

m

via Einstein's mass-energy relation,

E = m_{e} c^{2}

. In this model,

R

is approximately (

m_{e} = 9.1 \times 10^{- 31} kg, c = 3 \times 10^{8} m s^{- 1}

\frac{1}{4 π ε_{0}} = 9 \times 10^{9} F m^{- 1}

, magnitude of the electronic charge

= 1.6 \times 10^{- 19} C

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#2>Q 12

A stream of photons having energy

3 eV

each impinges on a potassium surface. The work function of potassium is

2.3 eV

. The emerging photoelectrons are slowed down by a copper plate placed

5 mm

away. If the potential difference between the two metal plates is

1 V

, the maximum distance the electrons can move away from the potassium surface before being turned back is,

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#2>Q 13

In a photocell circuit, the stopping potential $V_{0}$ is a measure of the maximum kinetic energy of the photoelectrons. The following graph shows experimentally measured values of stopping potential versus frequency $(ν)$ of incident light.

Question Image

The values of Planck's constant and the work function as determined from the graph are (taking the magnitude of electronic charge to be, $e = 1.6 \times 10^{- 19} C$ ),

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#2>Q 14

Photons of energy

7 eV

are incident on two metals

A

and

B

with work functions

6 eV

and

3 eV

, respectively. The minimum de-Broglie wavelengths of the emitted photoelectrons with maximum energies are

λ_{A}

and

λ_{B}

, respectively, where

\frac{λ_{A}}{λ_{B}}

is nearly,

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#2>Q 15

A singly ionised helium atom in an excited state

(n = 4)

emits a photon of energy

2.6 eV

. Given that the ground state energy of hydrogen atom is

- 13.6 eV

, the energy

(E_{t})

and quantum number

(n)

of the resulting state are, respectively,

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#2>Q 16

160 W

light source is radiating light of wavelength

6200 \overset{°}{A}

uniformly in all directions. The photon flux at a distance of

1.8 m

is of the order of (Planck's constant

= 6.63 \times 10^{- 34} J s)

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#2>Q 17

The wavelength of the first Balmer line caused by a transition from the

n = 3

level to the

n = 2

level in hydrogen is

λ_{1}

. The wavelength of the line caused by an electronic transition from

n = 5

n = 3

is,

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Practice Book for KVPY Aptitude Test - Stream SX Physics>Chapter 11 - Modern Physics - I>Exercise#2>Q 18

1.5 kW

(kilo-watt) laser beam of wavelength

6400 \overset{\circ}{A}

is used to levitate a thin aluminium disk of same area as the cross-section of the beam. The laser light is reflected by the aluminium disk without any absorption. The mass of the foil is close to,

The quantum hall resistance RH is a fundamental constant with the dimensions of resistance. If h is Planck's constant and e is the electronic charge, then the dimension of RH is the same as,

Important Questions on Modern Physics - I

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The quantum hall resistance $R_{H}$ is a fundamental constant with the dimensions of resistance. If $h$ is Planck's constant and $e$ is the electronic charge, then the dimension of $R_{H}$ is the same as,