A photon and an electron have same de-Broglie wavelength ≈ 10 - 10 m . Compare the kinetic energy of the electron with the (total) energy of the photon.

We know that expression for kinetic energy of an electron of mass m moving with velocity v is K = 1 2 m v 2 Its de-Broglie wavelength, λ = h m v ⇒ v = h λ m ∴ K = h 2 2 m λ 2 . We know that energy E of a photon of same wavelength λ as of electron is E = h c λ Hence ∴ K E = h 2 × λ 2 m λ 2 × h c = h 2 m λ c = 6 .6 × 10 − 34 Js 2 × 9 × 10 − 31 kg × 10 − 10 m × 3 × 10 8 ms − 1 = 0 . 012 < 1 . The kinetic energy of electron is less than the energy of photon.

E M B I B E

ISC Physics Class 12, Part-2>Chapter 11 - Matter Waves>QUESTIONS>Q 4

MEDIUM

12th ICSE

IMPORTANT

Earn 100

Show that the wavelength of electromagnetic radiation is equal to the de-Broglie wavelength of its quantum (photon).

Important Questions on Matter Waves

EASY

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 11 - Matter Waves>QUESTIONS>Q 5

de-Broglie wavelength of electrons of kinetic energy

E

is

λ

. What will be its value if kinetic energy of electrons is made

4 E

?

EASY

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IMPORTANT

ISC Physics Class 12, Part-2>Chapter 11 - Matter Waves>QUESTIONS>Q 6

An electron and a proton have the same kinetic energy. Which one has greater de-Broglie wavelength? Give formula.

EASY

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IMPORTANT

ISC Physics Class 12, Part-2>Chapter 11 - Matter Waves>QUESTIONS>Q 7

An electron and a proton have the same de-Broglie wavelength. Which one has higher kinetic energy? Which one is moving faster?

MEDIUM

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 11 - Matter Waves>QUESTIONS>Q 8

A photon and an electron have same de-Broglie wavelength

(\approx 10^{- 10} m)

. Compare the kinetic energy of the electron with the (total) energy of the photon.

HARD

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 11 - Matter Waves>QUESTIONS>Q 9

A proton and an alpha particle have been accelerated through the same potential difference. Compute the ratio of their de-Broglie wavelengths.

EASY

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IMPORTANT

ISC Physics Class 12, Part-2>Chapter 11 - Matter Waves>QUESTIONS>Q 10

Describe in brief what is observed when moving electrons are allowed to fall on a thin graphite film and the emergent beam falls on a fluorescent screen.

EASY

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IMPORTANT

ISC Physics Class 12, Part-2>Chapter 11 - Matter Waves>QUESTIONS>Q 1

What is de-Broglie hypothesis?

EASY

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 11 - Matter Waves>QUESTIONS>Q 1

What conclusion can be drawn from Davisson and German's experiment?