Karnataka PUC II Dual Nature of Radiation and Matter — practice questions — page 4

Explore 98 free Dual Nature of Radiation and Matter questions in Karnataka PUC II Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Dual Nature of Radiation and Matter questions and exercises with answers

Showing questions 91–98 of 98.

Worked practice questions

The de Broglie wavelength of a fast electron is comparable with:

Radio wavelengths
Sound wavelengths
Ocean wavelengths
X-ray wavelengths

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Correct answer: D. X-ray wavelengths

1. An electron's momentum is large for its mass. 2. A large momentum means a very short wavelength. 3. It comes out comparable with X-ray wavelengths. 4. So the answer is X-ray wavelengths. _Source: syllabus Physics, Ch 11 'Dual Nature of Radiation and Matter'_

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Set by intensity or by frequency?

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Left

Intensity

Items

Item
Photon count
Answer
Intensity
Item
Saturation current
Answer
Intensity
Item
Electrons per sec
Answer
Intensity
Item
Energy per photon
Answer
Frequency
Item
Stopping potential
Answer
Frequency
Item
Emission or not
Answer
Frequency

Right

Frequency

Instructions

Swipe left for intensity, right for frequency.

_Source: syllabus Physics, Ch 11 'Dual Nature of Radiation and Matter'_

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The momentum carried by a photon of wavelength $\lambda$ is

$h\lambda$
$\dfrac{h}{\lambda}$
$\dfrac{\lambda}{h}$
$h\lambda c$

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Correct answer: B. $\dfrac{h}{\lambda}$

1. A photon has energy $E = h\nu$ and, since it is massless, $E = pc$ where $c$ is the speed of light. 2. Equate: $pc = h\nu$, so $p = \dfrac{h\nu}{c}$. 3. Using $c = \nu\lambda$ gives $p = \dfrac{h\nu}{\nu\lambda} = \dfrac{h}{\lambda}$. 4. The same expression $p = h/\lambda$ is also what de Broglie applied to MATTER. Option A has wrong dimensions ($h\,\lambda$ would have units of action·length). Option C is the reciprocal. **Option D has an extra factor of $c\lambda$.** _Source: syllabus Physics Part 2, Ch 11, §11.7 "Particle Nature of Light: The Photon" + §11.8 (de Broglie hypothesis), pp. 9–11._

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