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1. Questions & answers of
blackbody & its radiation
BY JAYAM CHEMISTRY ADDA

2. 01. What is a blackbody?
01.
A.
B.
C.
Answer:
A rigid solid enclosure
Explanation:
A celestial object
A chemical substance
A rigid solid enclosure
A hollow solidified enclosure
having an opaque surface with
a pinhole is an assumption of a
perfect blackbody by the
physicist Gustav Kirchhoff.
Jayam chemistry adda

3. 02. Which of the following is not an example of a partial blackbody?
02.
A.
B.
C.
Answer:
Thin gold foil
Explanation:
Heating filament of a toaster
Thin gold foil
Platinum black
A perfect blackbody is unreal. All
earthly objects with absorbing
abilities greater than 0.95 are
imperfect blackbodies called
grey bodies. Thin gold foil
absorbing ability is much less
than the said value. Hence, it is
not an example of a partial
blackbody.
Jayam chemistry adda

4. 03. A blackbody emits_________
03.
A.
B.
C.
Answer:
Heat-assimilated electromagnetic
radiations
Explanation:
Heat-assimilated electromagnetic
radiations
Thermal radiations
Light radiations
The thermal electromagnetic
radiation emitted from a
blackbody is known as blackbody
radiation. A blackbody emits the
absorbed electromagnetic light
only on heating. Hence, it is a
heat-combined electromagnetic
radiation.
Jayam chemistry adda

5. 04. Which of the following substance has the highest absorbing power?
04.
A.
B.
C.
Answer:
Lamp black
Explanation:
Polished Silver
Diamond
Lamp black
Lamp black is a partial blackbody
with 0.98 absorbing power. It
implies lamp black can intake
98% of the incident that falls on
its surface. The diamond and
polished silver are not partial
blackbodies whose absorbing
capacities lie below 0.95.
Jayam chemistry adda

6. 05. What is the emissivity of a pure copper filament?
05.
A.
B.
C.
Answer:
Less than one
Explanation:
Less than one
Greater than one
Equal to one
When an object and a perfect
blackbody are at a fixed
temperature state, their radiant
emittances ratio is called
emissivity. Anyhow the emissivity
of an ideal blackbody is always
one. But all other earthly
materials' emissivity lies below
one.
Jayam chemistry adda

7. 06. Which of the following is an application of blackbody radiation?
06.
A.
B.
C.
Answer:
Burglar alarm
Explanation:
Cellular communications
Satellite communications
Burglar alarm
A burglar alarm is a security
device with a loud alarm to
alert about the opening of
doors and windows. It consists
of blackbody radiation
detectors and sensors that
connect with the control panel
systems.
Jayam chemistry adda

8. 07. Blackbody radiations comprise _____________
07.
A.
B.
C.
Answer:
Photons
Explanation:
Protons
Photons
Positrons
Following Planck's law,
blackbody radiation comprises
discrete radiant energy
particles called photons.
Jayam chemistry adda

9. 08. The following are examples of hot bodies identical in every respect in thermal
equilibrium conditions. Which one among them cools last?
08.
A.
B.
C.
Answer:
A solid sphere
Explanation:
A solid cube
A solid sphere
A solid cone
The rate of thermal emissions of
a blackbody varies directly with
its surface area. Objects with a
large surface area have high
emissive power. The solid
sphere has a low surface area
than the other hot bodies.
Hence, it cools last.
Jayam chemistry adda

10. 09. What is the color of blackbody radiation?
09.
A.
B.
C.
Answer:
It depends upon the enclosure's
temperature
Explanation:
Red
Blue
It depends upon the enclosure's
temperature
The color of blackbody radiation depends only
on the enclosure's temperature. The blackbody
radiation exhibit colors when its wavelength lies
between 350-750 nm, and the enclosure's
temperature ranges between 3800-8300 Kelvin
approximately. Initially, at 3800 K, the radiation
appears in dull red. At higher temperatures, the
radiation color follows the reverse VIBGYOR
pattern. Finally, the radiation becomes violet-
colored at 8257 Kelvin. At above 12000 K, the
radiation becomes white. Then it enters the
ultraviolet region part of the spectrum with
further temperature rise.
Jayam chemistry adda

11. 10. Which of the following surfaces are good reflectors of blackbody
radiations?
10.
A.
B.
C.
Answer:
Polished surfaces
Explanation:
Black coarse surfaces
Polished surfaces
Rough surfaces
Polished surfaces are even that
makes them better reflectors of
light. They reflect light parallel
to the incident light ray.
Jayam chemistry adda

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Visit our blog article on MCQs of blackbody & its radiation for
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https://jayamchemistrylearners.blogspot.com/2022/11/blackbody
-radiation-mcqs-answers-jayam.html

13. 11. Intensity of blackbody radiation is maximum at____________
11.
A.
B.
C.
Answer:
λmax
Explanation:
Longer radiation wavelengths
Shorter radiation wavelengths
λmax
The blackbody curve depicts that
energy distribution is not uniform over
broad wavelength ranges. As a result,
the blackbody radiation intensity rises
with emissive power at shorter
wavelengths. It continues until it
reaches the peak wavelength position
λmax. For a fixed temperature T, the
radiation intensity is maximum at
λmax.
Jayam chemistry adda

14. 12. The blackbody curve is the variation of ______ and ______
12.
A.
B.
C.
Answer:
Emissive power and wavelength
Explanation:
Emissive power and temperature
Emissive power and wavelength
Temperature and wavelength
A blackbody curve is a graph between
blackbody radiations' emissive power and
their wavelength at fixed temperature
conditions. The blackbody radiation
graph is a hill-shaped curve depicting
non-uniform spectral energy densities of
blackbody radiation emissions. Moreover,
the crest position of the blackbody curve
shifts towards shorter wavelengths at
higher temperatures by Wien's
displacement law.
Jayam chemistry adda

15. 13. Blackbody spectrum is a _______________spectrum
13.
A.
B.
C.
Answer:
Continuous radiation emission spectrum
Explanation:
Continuous radiation emission
Discontinuous radiation absorption
Line spectra of emitted blackbody
radiations
The blackbody spectrum is a patterned
arrangement of blackbody radiation
emissions in the increasing order of
frequencies or in the decreasing order of
their wavelengths. Besides, it is a continuous
emission spectrum due to the absence of
distinct boundary separation between the
spectral bands. In the blackbody spectrum,
one spectral band merges into the other
without partition. Like the electromagnetic
spectrum, it is a never-ending blackbody
radiation emission spectrum.
Jayam chemistry adda

16. 14. By Lambert's law, the distribution of blackbody radiation in
various directions is __________
14.
A.
B.
C.
Answer:
Identical
Explanation:
Identical
Irregular
Intermittent
Blackbody radiation emissions
are homogeneous in all
directions. Hence, they are
isotropic.
Jayam chemistry adda

17. 15. The blackbody emissions obey __________law
15.
A.
B.
C.
Answer:
Quantum law
Explanation:
Quantum law
Energy conservation law
Biot-savart law
Planck's quantum law was the first theory
that invented the particle character of
energy. And it successfully explained the
energy distributions of blackbody curves for
shorter and longer radiation wavelengths,
unlike Rayleigh-Jeans law and Wien
displacement law. It elucidated the
interaction of electromagnetic radiations
with the matter. Further, it calculated the
magnitude of blackbody emission energies
from the radiation frequencies.
Jayam chemistry adda

18. Thank you