The potential difference between the cathode and the target electrode in a Coolidge tube is changed from 20 kV to 30 kV . By what percent the minimum wavelength of the emitted X-rays will change?

When electrons accelerated through a potential difference V Strike a target, the maximum frequency of the emitted X-rays is given by eV = hv max Where, e Is charge of the electron and h The Planck constant. But v max = c λ min ∴ eV = hc λ min OR λ min = hc eV And hc e = k Constant Then, λ min = k v ∴ λ min 1 = k 20 . . . . . . . . . . . . ( i ) And λ min 2 = k 30 . . . . . . . . . . . . . . . . . . . ( ii ) So, the change is ∆ λ min = λ min 2 - λ min 1 ∆ λ min = k 30 - k 20 = - k 60 Then for percent the minimum wavelength of the emitted X-rays will change ∆ λ min λ min 1 × 100 = - k 60 k 20 × 100 = - 20 60 × 100 = - 33 . 3 % = 33 . 3 %

MEDIUM

12th West Bengal Board

IMPORTANT

Earn 100

Calculate the minimum wavelength of X-rays produced by an X -ray tube operating at $30 kV . [h = 6.6 \times 10^{- 27} erg . c]$

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

EASY

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 19 - Photoelectric Emission and Production and Properties of X-Rays>EXERCISE 19>Q 18

The potential difference across an X -ray tube is

12.4 kV

and the current through the filament is

2 mA .

Calculate the number of electrons striking per second on the anode

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 19 - Photoelectric Emission and Production and Properties of X-Rays>EXERCISE 19>Q 18

The potential difference across an X -ray tube is

12.4 kV

and the current through the filament is

2 mA .

Calculate the speed with which the electron strikes the target

EASY

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 19 - Photoelectric Emission and Production and Properties of X-Rays>EXERCISE 19>Q 18

The potential difference across an X -ray tube is

12.4 kV

and the current through the filament is

2 mA .

Calculate the shortest wavelength of X -rays emitted.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 19 - Photoelectric Emission and Production and Properties of X-Rays>EXERCISE 19>Q 19

The potential difference between the cathode and the target electrode in a Coolidge tube is changed from

20 kV

30 kV

. By what percent the minimum wavelength of the emitted X-rays will change?

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 19 - Photoelectric Emission and Production and Properties of X-Rays>EXERCISE 19>Q 20

When a beam of

10.6 eV

photons of intensity

2.0 W / m^{2}

falls on a platinum surface of area

1.0 \times 10^{- 4} m^{2}

and work function

5.6 eV, 0.53 %

of the incident photons eject photoelectrons. Find the number of photoelectrons emitted per second and their minimum and maximum energies (in

eV

). Take

1 eV = 1.6 \times 10^{- 19} J

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 19 - Photoelectric Emission and Production and Properties of X-Rays>EXERCISE 19>Q 21

A silver sphere of radius

1 cm

and work function

4.7 eV

is suspended from an insulating thread in free space. It is under continuous illumination of

200 nm

wavelength light. As photoelectrons are emitted, the sphere get charged and acquires a potential. The maximum number of photoelectrons emitted from the sphere is

A \times 10^{Z}

(where

1 ⟨ A < 10

). Find the value of Z.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 19 - Photoelectric Emission and Production and Properties of X-Rays>EXERCISE 19>Q 22

A monochromatic beam of light is falling normally on a surface having reflection co-efficient

0.25

and absorption coefficient

0.75

. The pressure exerted by the beam of light on the surface is

5 \times 10^{- 7} {Nm}^{- 2}

. The wavelength of light is

490 nm

. Find the number of photons falling per unit area per second on the surface.

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 19 - Photoelectric Emission and Production and Properties of X-Rays>EXERCISE 19>Q 1

The photoelectric threshold wavelength for which for silver is

λ_{0}

. The energy of the electron ejected from the surface of silver by an incident wavelength

λ (λ < λ_{0})

will be

Calculate the minimum wavelength of X-rays produced by an X -ray tube operating at 30kV.h=6.6×10-27erg.c

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

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Calculate the minimum wavelength of X-rays produced by an X -ray tube operating at $30 kV . [h = 6.6 \times 10^{- 27} erg . c]$