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Class 12
Physics
Dual Nature Of Radiation And Matter
light of frequency 7 21 times 1014 hz is inciden...

Question:
Light of frequency 7.21 × 10¹⁴ Hz is incident on a metal surface. Electrons with a maximum speed of 6.0 × 10⁵ m/s are ejected from the surface. What is the threshold frequency for photoemission of electrons?

Answer:

Frequency of the incident photon, v = 488 nm = 488 x 10^-9 m

Maximum speed of the electrons, v = 6.0 × 10⁵ m/s

Planck’s constant, h = 6.626 × 10⁻³⁴ Js

Mass of an electron, m = 9.1 × 10⁻³¹ kg

For threshold frequency ν0, the relation for kinetic energy is written as: 1/2 mv²

= h(v - v₀)

∴ v₀ = v - mv²/2h

= 7.21 x 10¹⁴ - (9.1 x 10^-31) x (6 x 10⁵)² / 2 x (6.626 x 10^-34)

= 7.21 x 10¹⁴ - 2.472 x 10¹⁴

= 4.738 x 10¹⁴ Hz

Therefore, the threshold frequency for the photoemission of electrons is 4.738 × 10¹⁴ Hz.

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Question:
Light of frequency 7.21 × 10¹⁴ Hz is incident on a metal surface. Electrons with a maximum speed of 6.0 × 10⁵ m/s are ejected from the surface. What is the threshold frequency for photoemission of electrons?

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Question: Light of frequency 7.21 × 1014 Hz is incident on a metal surface. Electrons with a maximum speed of 6.0 × 105 m/s are ejected from the surface. What is the threshold frequency for photoemission of electrons?

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Question:
Light of frequency 7.21 × 10¹⁴ Hz is incident on a metal surface. Electrons with a maximum speed of 6.0 × 10⁵ m/s are ejected from the surface. What is the threshold frequency for photoemission of electrons?