Tiwari Academy Discussion

Ashok0210

Asked: April 27, 2021In: Class 12 Physics

(a) A monoenergetic electron beam with electron speed of 5.20 × 10⁶ m s⁻¹ is subject to a magnetic field of 1.30 × 10⁻⁴ T normal to the beam velocity. What is the radius of the circle traced by the beam, given e/m for electron equals 1.76 × 10¹¹C kg⁻¹. (b) Is the formula you employ in (a) valid for calculating radius of the path of a 20 MeV electron beam? If not, in what way is it modified? [Note: Exercises 11.20(b) and 11.21(b) take you to relativistic mechanics which is beyond the scope of this book. They have been inserted here simply to emphasise the point that the formulas you use in part (a) of the exercises are not valid at very high speeds or energies. See answers at the end to know what ‘very high speed or energy’ means.]

Class 12 Physics CBSE and UP Board Dual Nature of Radiation and Matter Chapter-11 Exercise 11.21 NCERT Solutions for Class 12 Physics Chapter 11 Question-21 Additional Exercise

Ashok0210

Asked: April 27, 2021In: Class 12 Physics

Answer the following questions: (a) Quarks inside protons and neutrons are thought to carry fractional charges [(+2/3)e ; (–1/3)e]. Why do they not show up in Millikan’s oil-drop experiment? (b) What is so special about the combination e/m? Why do we not simply talk of e and m separately? (c) Why should gases be insulators at ordinary pressures and start conducting at very low pressures? (d) Every metal has a definite work function. Why do all photoelectrons not come out with the same energy if incident radiation is monochromatic? Why is there an energy distribution of photoelectrons? (e) The energy and momentum of an electron are related to the frequency and wavelength of the associated matter wave by the relations: E = h ν, p = h/λ But while the value of λ is physically significant, the value of ν (and therefore, the value of the phase speed ν λ) has no physical significance. Why?

Class 12 Physics CBSE and UP Board Dual Nature of Radiation and Matter Chapter-11 Exercise 11.37 NCERT Solutions for Class 12 Physics Chapter 11 Question-37 Additional Exercise

Ashok0210

Asked: April 27, 2021In: Class 12 Physics

Compute the typical de Broglie wavelength of an electron in a metal at 27 ºC and compare it with the mean separation between two electrons in a metal which is given to be about 2 × 10⁻¹⁰ m. [Note: Exercises 11.35 and 11.36 reveal that while the wave-packets associated with gaseous molecules under ordinary conditions are non-overlapping, the electron wave-packets in a metal strongly overlap with one another. This suggests that whereas molecules in an ordinary gas can be distinguished apart, electrons in a metal cannot be distintguished apart from one another. This indistinguishibility has many fundamental implications which you will explore in more advanced Physics courses.]

Class 12 Physics CBSE and UP Board Dual Nature of Radiation and Matter Chapter-11 Exercise 11.36 NCERT Solutions for Class 12 Physics Chapter 11 Question-36 Additional Exercise

Ashok0210

Asked: April 27, 2021In: Class 12 Physics

Find the typical de Broglie wavelength associated with a He atom in helium gas at room temperature (27 ºC) and 1 atm pressure; and compare it with the mean separation between two atoms under these conditions.

Class 12 Physics CBSE and UP Board Dual Nature of Radiation and Matter Chapter-11 Exercise 11.35 NCERT Solutions for Class 12 Physics Chapter 11 Question-35 Additional Exercise

Ashok0210

Asked: April 27, 2021In: Class 12 Physics

The wavelength of a probe is roughly a measure of the size of a structure that it can probe in some detail. The quark structure of protons and neutrons appears at the minute length-scale of 10⁻¹⁵ m or less. This structure was first probed in early 1970’s using high energy electron beams produced by a linear accelerator at Stanford, USA. Guess what might have been the order of energy of these electron beams. (Rest mass energy of electron = 0.511 MeV.)

Class 12 Physics CBSE and UP Board Dual Nature of Radiation and Matter Chapter-11 Exercise 11.34 NCERT Solutions for Class 12 Physics Chapter 11 Question-34 Additional Exercise

Ashok0210

Asked: April 27, 2021In: Class 12 Physics

A 100W sodium lamp radiates energy uniformly in all directions. The lamp is located at the centre of a large sphere that absorbs all the sodium light which is incident on it. The wavelength of the sodium light is 589 nm. (a) What is the energy per photon associated with the sodium light? (b) At what rate are the photons delivered to the sphere?

Class 12 Physics CBSE and UP Board Dual Nature of Radiation and Matter Chapter-11 Exercise 11.7 NCERT Solutions for Class 12 Physics Chapter 11 Question-7

Ashok0210

Asked: April 27, 2021In: Class 12 Physics

(a) For what kinetic energy of a neutron will the associated de Broglie wavelength be 1.40 × 10⁻¹⁰ m? (b) Also find the de Broglie wavelength of a neutron, in thermal equilibrium with matter, having an average kinetic energy of (3/2) k T at 300 K

Class 12 Physics CBSE and UP Board Dual Nature of Radiation and Matter Chapter-11 Exercise 11.17 NCERT Solutions for Class 12 Physics Chapter 11 Question-17

Ashok0210

Asked: April 27, 2021In: Class 12 Physics

An electron and a photon each have a wavelength of 1.00 nm. Find (a) their momenta, (b) the energy of the photon, and (c) the kinetic energy of electron

Class 12 Physics CBSE and UP Board Dual Nature of Radiation and Matter Chapter-11 Exercise 11.16 NCERT Solutions for Class 12 Physics Chapter 11 Question-16

Ashok0210

Asked: April 27, 2021In: Class 12 Physics

What is the de Broglie wavelength of (a) a bullet of mass 0.040 kg travelling at the speed of 1.0 km/s, (b) a ball of mass 0.060 kg moving at a speed of 1.0 m/s, and (c) a dust particle of mass 1.0 × 10⁻⁹ kg drifting with a speed of 2.2 m/s?

Class 12 Physics CBSE and UP Board Dual Nature of Radiation and Matter Chapter-11 Exercise 11.15 NCERT Solutions for Class 12 Physics Chapter 11 Question-15

Ashok0210

Asked: April 27, 2021In: Class 12 Physics

The wavelength of light from the spectral emission line of sodium is 589 nm. Find the kinetic energy at which (a) an electron, and (b) a neutron, would have the same de Broglie wavelength.

Class 12 Physics CBSE and UP Board Dual Nature of Radiation and Matter Chapter-11 Exercise 11.14 NCERT Solutions for Class 12 Physics Chapter 11 Question-14

Find the typical de Broglie wavelength associated with a He atom in helium gas at room temperature (27 ºC) and 1 atm pressure; and compare it with the mean separation between two atoms under these conditions.

(a) For what kinetic energy of a neutron will the associated de Broglie wavelength be 1.40 × 10⁻¹⁰ m? (b) Also find the de Broglie wavelength of a neutron, in thermal equilibrium with matter, having an average kinetic energy of (3/2) k T at 300 K

An electron and a photon each have a wavelength of 1.00 nm. Find (a) their momenta, (b) the energy of the photon, and (c) the kinetic energy of electron

What is the de Broglie wavelength of (a) a bullet of mass 0.040 kg travelling at the speed of 1.0 km/s, (b) a ball of mass 0.060 kg moving at a speed of 1.0 m/s, and (c) a dust particle of mass 1.0 × 10⁻⁹ kg drifting with a speed of 2.2 m/s?

The wavelength of light from the spectral emission line of sodium is 589 nm. Find the kinetic energy at which (a) an electron, and (b) a neutron, would have the same de Broglie wavelength.

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