# Biophysics Questions and Answers – Scattering

This set of Biophysics Multiple Choice Questions & Answers (MCQs) focuses on “Scattering”.

1. To count bacterial cell numbers, we measure the absorbance by bacterial cell at 600 nm in UV visible spectroscopy.
a) True
b) False

Explanation: During bacterial cell count assay spectrophotometricly, we pass the bacterial culture through 600 nm wavelength light. At this absorbance, most of the light gets transmitted by bacterial cell wall components. So this phenomenon is a scattering phenomenon rather than an absorbance phenomenon.

2. Light scattering can be used to determine which of the following option?
a) Molecular weight
b) Viscosity
c) Shape
d) Chemical property

Explanation: Actually it’s an indirect technique because if the size is less that means the molecular weight of the particle is less and vice versa. Now, viscosity does not contribute anything in scattering of light. Scattering solely depends on the size of the molecule, chemical property cannot be inferred from this property.

3. Suppose a solution contains numerous particle (can be protein, lipid or anything) of a diameter of x unit. Now, which of the following light will be scattered more?
a) The lights with the wavelength greater than x unit will be scattered more
b) The lights with the wavelength x unit will be scattered more
c) The lights with the wavelength less than x unit will be scattered more
d) It will not scatter any light rather it will absorb all the light

Explanation: It is the property of light. The particle which is used to be scattering must be very small and the wavelength it scatters is smaller than its size. Most of the wavelength, which is higher than the size of the particle are not scattered rather transmitted through the medium.

4. Among the following options, which one is not the use of light scattering?
a) Protein X ray crystallography
b) Bacterial cell count
c) Tindal effect
d) Protein NMR study

Explanation: In NMR, the molecular or protein structure is revealed by locating the H atom and Carbon atom. This procedure does not use any kind of scattering method. The rest of the methods works on scattering principle.

5. Which technique uses Scattering to reveal an unknown protein structure?
a) NMR
b) X ray crystallography
c) CD spectrophotometry
d) Fluorescence spectrophotometry

Explanation: In X-ray crystallography, we first make a protein crystal and followed by its purification, we place it in front of laser light and observe the scattering of light. Observing the scattering pattern, the molecular structure is predicted. NMR does not use scattering. CD and Fluorescence are used to quantify proteins not used to determine the structure.

6. If the scattering phenomenon was not there in nature, what would be the color of Sky?
a) White
b) Black
c) Blue
d) Red

Explanation: If Scattering was not there in the nature, then sunlight would directly enter into the earth. We would be able to see all the elements present in earth but the sky will be black due to the absence of any light. We see the sky as blue because of the scattering phenomenon by dust particles present in air.

7. The white color of the cloud is best explained by which of the following type of scattering?
a) Rayleigh scattering
b) Red light scattering
c) Blue light scattering
d) Mie Scattering

Explanation: This phenomenon is named after the scientist, who invented this phenomenon. He told that cloud contains many big particle and water droplets which can scatter all the wavelengths of visible lights present in nature. Therefore, cloud seems to be white.

8. The reason behind the blue color appearance of the sky was first experimentally best explained by Prof. _________
a) Rayleigh
b) Mie
c) Delbert
d) John Tyndall

Explanation: Rayleigh and Mie, later explained the natural scattering phenomenon properly. But at first John Tyndall first experimentally proved the phenomenon of scattering and the reason of the blue appearance of sky.

9. Among the following, which properties light scattering?
a) Small size of the molecule
b) Large size of the molecule
c) The size of the particle does not even matter
d) Molecular weight of the particle

Explanation: Yes, scattering only depends on the size of the particle. If the size is very small then only it can scatter light with lower wavelength.

10. Suppose you have a small opalescent glass stone and you kept it under sunlight (white light) during the afternoon. The light is transmitting through the stone and touching the ground on a point A. Among the following option which one is possible based on light scattering concept?
a) The stone will be red in color and point A will be blue in color
b) The stone will be orange in color and the point A will be violet in color
c) The stone will be blue in color and the point A will be orange in color
d) The stone will be orange in color and the transmitting light at the point A will be green in color

Explanation: This experiment is originally performed by John Tyndall. In scattering, smaller wavelength of lights gets scattered but higher wavelength of light mostly don’t gets scatter as their wavelength is larger than most of the molecule. Now, only in option C, the stone blue because of lower wavelength blue color is getting scatted and rest of the light is transmitting. Therefore, the point A is orange. In the rest of the cases, higher wavelength light was getting scattered and lower wavelength light was getting transmitted.

Sanfoundry Global Education & Learning Series – Biophysics.

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