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Answered on 07 Jan CBSE/Class 12/Science/Physics Tuition/Class XI-XII Tuition (PUC)

Akash Pandey

Physics Tutor

Expressions for the electric and magnetic fields in free space contain the electric permittivity ε0 and magnetic permeability μ0 of free space. These two quantities are not independent but are related to "c", the speed of light and other electromagnetic waves. The magnetic constant μ0 =... read more

Expressions for the electric and magnetic fields in free space contain the electric permittivity ε0 and magnetic permeability μ0 of free space. These two quantities are not independent but are related to "c", the speed of light and other electromagnetic waves. The magnetic constant μ0 = 4π x 10-7 T m/A is called the permeability of space. The permeabilities of most materials are very close to μ0 since most materials will be classified as either paramagnetic or diamagnetic. But in ferromagnetic materials the permeability may be very large and it is convenient to characterize the materials by a relative permeability.
This contains the force unit N for Newton and the unit A is the Ampere, the unit of electric current.

With the magnetic permeability established, the electric permittivity takes the value given by the relationship

c = 1/sqrt(ε0μ0)

where the speed of light is given by

c=2.99792458 x 10^8 m/s (exact)

This gives a value of free space permittivity

ε0 = 8.854187817 x 10^-12 F/m

which in practice is often used in the form

k = 1/4piε0 = 8.987552 X10^9 Nm^2/C^2 = Coulomb's constant

These expressions contain the units F for Farad, the unit of capacitance, and C for Coulomb, the unit of electric charge.

The electric permittivity is connected to the energy stored in an electric field. It is involved in the expression for capacitance because it affects the amount of charge which must be placed on a capacitor to achieve a certain net electric field. In the presence of a polarizable medium, it takes more charge to achieve a given net electric field and the effect of the medium is often stated in terms of a relative permittivity.

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Answered on 02 Feb CBSE/Class 12/Science/Physics Tuition/Class XI-XII Tuition (PUC)

Name the phenomenon which shows the quantum nature of electromagnetic radiation.

Bhojraj Sharma

Tutor

Photoelectric effect
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Answered on 05 Mar CBSE/Class 12/Science/Physics Tuition/Class XI-XII Tuition (PUC)

Write the principle of working of a metre bridge.

Physics Teacher

wheatstone bridge principle. here p/q=r/s.p=unknown resistance,q=resistance of the resistance box given to the circuit.if l=length of the slide wire at which when tip of the jockey touches it gives zero deflection in the galvanometer,then r=l and s=100-l. so p=q(l/100-l). read more

wheatstone bridge principle.

here p/q=r/s.p=unknown resistance,q=resistance of the resistance box given to the circuit.if l=length of the slide wire at which when tip of the jockey touches it gives zero deflection in the galvanometer,then r=l and s=100-l.

so p=q$imes$(l/100-l).

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Answered on 22 Feb CBSE/Class 12/Science/Physics Tuition/Class XI-XII Tuition (PUC)

Write the functions of the three segments of a transistor.

Diksha Marwaha

Tutor

Transistor consist of emitter,collector and base.each one is having a particular function . 1.)emitter emits the charge carriers . 2.)collector collects the charge carriers . 3)base provides interaction between emitter and. Collector.
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Answered on 01 Mar CBSE/Class 12/Science/Physics Tuition/Class XI-XII Tuition (PUC)

State the condition under which a large magnification can be achieved in an astronomical telescope.

D Mukherjee

Teacher

There is large magnification when the image formed by the objective is within the focal length of the eye pece of the telescope
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Answered on 23 Feb CBSE/Class 12/Science/Physics Tuition/Class XI-XII Tuition (PUC)

Electrons are emitted from the cathode of a photocell of negligible work function, when photons of wavelength... read more
Electrons are emitted from the cathode of a photocell of negligible work function, when photons of wavelength are incident on it. Derive the expression for the de Broglie wavelength of the electrons emitted in terms of the wavelength of the incident light. read less

Ramya

Primary Teacher

E=Φ+K.E max. Where: Φ=work function of electrode Given: Φ=0 ∴ E=K.E of electron where: E= incident energy. λ=h÷p. Where: h= plank cons. P= momentum K.E = (1÷2)mv* *=2 p= mv ∴ p=√2mK.E. Now put value in de- Broglie wavelength formula we... read more

E=Φ+K.E max.

Where: Φ=work function of electrode

Given: Φ=0

∴ E=K.E of electron where: E= incident energy.

λ=h÷p.

Where: h= plank cons.

P= momentum

K.E = (1÷2)mv*    *=2

p= mv

∴ p=√2mK.E.

Now put value in de- Broglie wavelength formula we get,

λ = h÷√2mK.E required and.

Where:λ= de Broglie wavelength

K.E= kinetic energy of electron.

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Answered on 20 Mar CBSE/Class 12/Science/Physics Tuition/Class XI-XII Tuition (PUC)

Derive the Bohr ??s quantisation condition for angular momentum of the orbiting of electron in hydrogen... read more
Derive the Bohrâ??s quantisation condition for angular momentum of the orbiting of electron in hydrogen atom, using de Broglieâ??s hypothesis. read less

Nitesh Rai

Tutor

In the Bohr model, the wavelength associated with the electron is given by DeBroglie relationship, and the standing wave condition that circumference = whole number of wavelengths. In the hydrogenic case, the number n is the principal quantum number. These can be combined to get an expression for the... read more

In the Bohr model, the wavelength associated with the electron is given by DeBroglie relationship,

and the standing wave condition that circumference = whole number of wavelengths. In the hydrogenic case, the number n is the principal quantum number.

These can be combined to get an expression for the angular momentum of the electron in orbit.

Thus L is not only conserved, but constrained to discrete values by the quantum number n. This quantization of angular momentum is a crucial result and can be used in determining the Bohr orbit radii and Bohr energies

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Answered on 09 Mar CBSE/Class 12/Science/Physics Tuition/Class XI-XII Tuition (PUC)

Explain the term, ??amplitude modulation ?? of a signal. For an amplitude modulated wave, the maximum... read more
Explain the term, â??amplitude modulationâ?? of a signal. For an amplitude modulated wave, the maximum amplitude is 10 V and the minimum amplitude is 2 V. Calculate the modulation index. read less

Jayabal S

Signal waves doesnot have the enegy to carry over a long ditance.so the signal waves are mixed wave mixed with high energy carrier waves by its ampltude.that is called amplitude modulation. Modulation index=change in amplitude/original amplitude=4/6=0.666
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Answered on 05 Mar CBSE/Class 12/Science/Physics

Do electromagnetic waves carry energy and momentum?

Ramya

Primary Teacher

An electromagnetic wave, although it carries no mass, does carry energy. It also has momentum, and can exert pressure (known as radiation pressure). The reason tails of comets point away from the Sun is the radiation pressure exerted on the tail by the light (and other forms of radiation) from sun
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Answered on 08 Mar CBSE/Class 12/Science/Physics

In Young ??s double slit experiment, the two slits are illuminated by two different lamps having same... read more
In Youngâ??s double slit experiment, the two slits are illuminated by two different lamps having same wavelength of light. Explain with reason, whether interference pattern will be observed on the screen or not. read less

Saurabh

Tutor

interference pattern will not be observed on the screen........because interference can only be occured when the source of light is coherent i.e both have constant phase difference..........Here light from two independent source(lamp) can not have constant phase difference.
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