Fsc part 2 online preparation for physics chapter 19 (modern physics)

Question # 1

State uncertainty principle.

Ans 1: The product of uncertainty in the measurement of momentum and uncertainty in the measurement of position of an electron is approximately equal to Planck's constant.
The product of uncertainty in the measurement of energy and uncertainty in the measurement of time of an electron is approximately equal to Planck's constant.

Question # 2

Does the dilation mean that time really passes more slowly in moving system or that it only seems to pass more slowly.Explain briefly.

Ans 1: According to dilation formula
t= $\scriptstyle {\sqrt {1-{\frac {v^{2}}{c^{2}}}}}$ "
This relation show that a clock moving with respect to an observe appears to move slow then it does when it is at rest with respecttohim.So the moving clocks just appears to run slowly to the observer at rest.Hence time dilation is an apparent change and it only seems to pass more slowly but not actually.

Question # 3

What are advantages of NAVSTAR navigation system?

Ans 1: NAVSTAR is used to locate the position and find the speed of an object anywhere on Earth up to to an accuracy of 2 cms^-1.

Question # 4

Define Stopping potential and Threshold frequency.

Ans 1: Stopping potential:The stopping potential is the potential difference applied to stop the electrons from being ejected from the surface when the light fall on it.
Threshold frequency:The minimum of frequency of incident light at which electrons are emitted from a surface is called threshold frequency.

Question # 5

If you are moving in a spaceship at very high speed relative to the earth.Would you notice difference(a)In your pulse rate(b)In the pulse rate of people on the earth?

Ans 1:
1. The pulse rate of the person inside the spaceship moving with large velociety will decrease.
2. The pulse rate of the people on the earth with respect to the person inside the spaceship with large velocity will increase.

Question # 6

Distinguished between photoelectric effect and Compton effect.

Ans 1: The emission of electron from a metal surface when exposed to suitable frequency light is called photoelectric effect and when x rays are scattered by loosely bound electrons from graphite target the phenomena of change in wavelength is known as compton effect.

Question # 7

When light shine on surface,is momentum transferred to metal surface?

Ans 1: Yes when light shine on surface,momentum is transferred to metal surface and also the energy.So metal is heated up.

Question # 8

Define ionization potential and excitation potential.

Ans 1: Ionization potential:The potential necessary to remove an electron from the atom is called ionization potential,It is expressed in volts.
Ans 2: Excitation potential:The potential require to raise orbital electron in atom from one energy level to an other is called excitation potential.

Question # 9

Photoelectric effect give the evidence of the particle nature of light,Explain it how?

Ans 1: If light were simple a wave like phenomena ,then increasing the intensity and thereby increasing the total energy failing on the surface would be expected to eventually provide enough energy to release electron no matter what the frequency .Furthermore in the classical picture one would expect the maximum energy of the emitted electrons to depend on the intensity of light--but it does not.So this is evidence that light behaves as if it were a particle.

Question # 10

Define Compton effect.Write formula of Compton shift for scattering angle.

Ans 1: When X-rays are scattered by loosely bound electrons from a graphite target,the phenomena of change in wavelength is known as Compton Effect.Compton shift for scattering angle is given
$\lambda '-\lambda ={\frac {h}{m_{e}c}}(1-\cos {\theta }),$

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Fsc part 2 online preparation for physics chapter 19 (modern physics)

Online Short Questions For Chapter 8 "12th Class Physics Chapter 8 Short Questions Preparation "

Physics - 12th Class Physics Chapter 8 Short Questions Preparation

State uncertainty principle.

Does the dilation mean that time really passes more slowly in moving system or that it only seems to pass more slowly.Explain briefly.

What are advantages of NAVSTAR navigation system?

Define Stopping potential and Threshold frequency.

If you are moving in a spaceship at very high speed relative to the earth.Would you notice difference(a)In your pulse rate(b)In the pulse rate of people on the earth?

Distinguished between photoelectric effect and Compton effect.

When light shine on surface,is momentum transferred to metal surface?

Define ionization potential and excitation potential.

Photoelectric effect give the evidence of the particle nature of light,Explain it how?

Define Compton effect.Write formula of Compton shift for scattering angle.

Prepare Complete Set Wise Questions For Chapter 8 "12th Class Physics Chapter 8 Short Questions Preparation "

Set 1

Set 2

Set 3

12th Class Physics Chapter 8 Short Questions Preparation - Set 1

State uncertainty principle.

Does the dilation mean that time really passes more slowly in moving system or that it only seems to pass more slowly.Explain briefly.

What are advantages of NAVSTAR navigation system?

Define Stopping potential and Threshold frequency.

If you are moving in a spaceship at very high speed relative to the earth.Would you notice difference(a)In your pulse rate(b)In the pulse rate of people on the earth?

Distinguished between photoelectric effect and Compton effect.

When light shine on surface,is momentum transferred to metal surface?

Define ionization potential and excitation potential.

Photoelectric effect give the evidence of the particle nature of light,Explain it how?

Define Compton effect.Write formula of Compton shift for scattering angle.

12th Class Physics Chapter 8 Short Questions Preparation - Set 2

What do you understand by work function and stopping potential?

Write at least two justification for light to behave as wave and as a particle.

What advantage of an electron microscope has over an optical microscope?

If you are moving in a spaceship at very high speed relative to the earth.Would you notice difference(a)In your pulse rate(b)In the pulse rate of people on the earth?

The rest mass of photon is zero.Is its momentum also zero?

State uncertainty principle.

Is it possible to create a single electron from energy?

Define Compton effect.Write formula of Compton shift for scattering angle.

What do you know by annihilation of matter?

Will higher frequency of light ejects greater number of electrons than low frequency of light?

12th Class Physics Chapter 8 Short Questions Preparation - Set 3

Photoelectric effect give the evidence of the particle nature of light,Explain it how?

Which has the lower energy quanta,radio waves or x rays?Explain

We do not notice the de-Broglie wavelength for a pitched cricket ball.Explain why?

λ =h/mv

Will higher frequency of light ejects greater number of electrons than low frequency of light?

What do you know by annihilation of matter?

What are the measurement on which two observers in relative motion will always agree upon?

State uncertainty principle.

Write at least two justification for light to behave as wave and as a particle.

A satellite is orbiting around earth.Is its frame of reference inertial or non-inertial ?Justify your answer.

When light shine on surface,is momentum transferred to metal surface?

12th Class Physics Ch 19 Preparation

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