Tag: option c: imaging

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Questions Related to option c: imaging

Multiple choice detection and recording of x-ray images option c: imaging physics

The apparent wavelength of the light from a star moving away from the earth is 0.2% more than its actual wavelength. Then the velocity of the star is 

  1. $6 \times 10^7 \ ms^{-1}$
  2. $6 \times 10^6 \ ms^{-1}$
  3. $6 \times 10^5 \ ms^{-1}$
  4. $6 \times 10^4 \ ms^{-1}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The Doppler shift formula for light is delta_lambda / lambda = v / c. Given delta_lambda / lambda = 0.2% = 0.002, then v = 0.002 * c. Using c = 3 * 10^8 m/s, v = 0.002 * 3 * 10^8 = 6 * 10^5 m/s.

Multiple choice detection and recording of x-ray images option c: imaging physics

From the $\alpha$-particle scattering experiment, Rutherford concluded that

  1. $\alpha$- particles can come within a distance of the order of $10^{-14}$ m of the nucleus.
  2. The radius of the nucleus is less than $10^{-14}$ m

  3. Scattering follows coulomb's law

  4. The positively charged parts of the atom move with extremely high velocities
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Rutherford's alpha-particle scattering experiment allowed him to estimate the distance of closest approach, which provided an upper bound for the radius of the nucleus, concluding it is less than 10^-14 m.

Multiple choice detection and recording of x-ray images option c: imaging physics

X-rays of wavelength of $22\ pm$ are scattered from a carbon target at an angle of $85^0$ to the incident beam. The compton shift for X-rays is $(cos\ 85^0=0.088)$

  1. $2.2\ pm$
  2. $1.1\ pm$
  3. $0.55\ pm$
  4. $4.4\ pm$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Compton shift is given as $\Delta \lambda =\dfrac{h}{mc}(1-cos \phi )=\dfrac{6.62\times 10^{-34}Js}{9.1\times 10^{-31} Kg\times 3\times 10^8m/s}(1-cos 85^0)$ 

where $m$ is the mass of electron and $h$ is Planck's constant with $c$ as speed of light in air.
On calculation we get the shift as $\Delta \lambda =2.2\times 10^{-12}meter=2.2pico meter$
Option A is correct.

Multiple choice detection and recording of x-ray images option c: imaging physics

Find the correct statement

  1. A free electron can absorb a photon completely.

  2. A free electron can not absorb a photon completely.

  3. A free electron can not exist.

  4. A free neutron can exist for a long time
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Compton's scattering 


$\displaystyle \Delta \lambda =\dfrac{h}{mc}(1-\cos \phi )$ 

which shows a free electron can not absorb a photon completely. If a free electron absorb a photon there is nothing to share the recoil. So momentum will not conserve which is not possible.
So, the answer is option (B).

Multiple choice detection and recording of x-ray images option c: imaging physics

For Compton effect with visible light the observed Compton shift is

  1. Very large because the electrons appear free

  2. Very small because the electrons appear free

  3. Is almost zero because the electrons appear bound

  4. Less than zero
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In compton scattering it is necessary that the energy of the photon should be very much greater than binding energy of electron. Binding energy is equal to work function of metal. In most of metals, the threshold frequency is equal to that of ultravoilet light that is why we do not observe comption effect with visible light.

Multiple choice detection and recording of x-ray images option c: imaging physics

A strong argument for the particle nature of cathode rays is that they

  1. travel through vacuum

  2. cast shadow

  3. get deflected by electric and magnetic field

  4. produce fluroscence
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The fact that cathode rays are deflected by electric and magnetic fields proves they consist of charged particles (electrons), as neutral waves would not be affected by these fields.

Multiple choice detection and recording of x-ray images option c: imaging physics

A photon of frequency f under goes compton scattering from an electron at rest and scatters through an angle $\theta$. The frequency of scattered photon is ${ f }^{ ' }$ then

  1. ${ f }^{ ' } > f$
  2. ${ f }^{ ' } = f$
  3. ${ f }^{ ' } < f$

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

After scattering the wavelength of scattered photon increases due to the loss of energy and hence, the frequency decreases.
So, $f'<f$
So, the answer is option (C).

Multiple choice detection and recording of x-ray images option c: imaging physics

The particle nature of cathode rays is proved by

  1. Their deflection under magnetic/ electric field

  2. Colour of glow in gas discharge tube.

  3. Their propagation along a straight line.

  4. All of these.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is essentially the same question as 431450. Cathode rays (electrons) have charge and mass, which is proven by their deflection in electric and magnetic fields. Option A is correct. Colour of glow (B) depends on gas, not cathode rays. Straight-line propagation (C) and all options (D) don't specifically prove particle nature.

Multiple choice detection and recording of x-ray images option c: imaging physics

If h is planks constant, $m _o$ is rest mass of electron and c is the speed of light in vacuum, the S.I unit of $\dfrac{h}{m _{0}C}$ is

  1. $A^{0}$

  2. Js

  3. Ns

  4. m
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

de Broglie wavelength,

$\lambda =\dfrac { h }{ p } =\dfrac { h }{ mv } $
and unit of $\lambda$ is $m$.
So, the answer is option (D).