When the disturbed electrons of an exited atom transfer back into lower energy levels they emit energy in the form of electromagnetic wave pulses called
neutrons
electrons
phonons
photons
Correct Answer :
D. photons
Related Questions
When light passes from air to glass, its velocity in glass
increases
decreases
remains unchanged
first decreases then increases
Who discovered that the Cree Call acceleration Is the same for any object at a given place?
Newton
Pascal
Archimedes
Galileo
At what temperature do the Fahrenheit and Celsius scales give the same reading?
212°
32°
-40°
0°
Some persons are not able to see distant objects clearly because the image of the object is focused in front of the retina. This defect is known as
short sight
long sight
astigmatism
presbyopia
Which is the densest planet of the solar system?
Sun
Jupiter
Mercury
Earth
Which of the following is fissionable?
U-234
U-235
U-238
Both (b) and (c)
The largest reserve of radioactive element which can be used in a nuclear reactor has been found in India, The name of the element is
Thorium
Uranium
Plutonium
Radium
When a steel ball is placed on the surface of mercury, it does not sink because
of the surface tension of mercury
mercury is a semi-solid
of the high viscosity of mercury
the density of mercury is greater than that of steel
The speed at which light travels in vacuum is
3 x 107 ms-1
5 x 108 ms-1
3 x 104 kms-1
3 x 108 ms-1
Changing of one element into another element is known as
transmutation
fission
fusion
radioactivity
A device used to measure heights above sea level is known as
altimeter
anemometer
dilatometer
potentiometer
The distance between two bodies is halved. Now the force of attraction between them will be
half
one fourth
four times
two times
Which of the following apparatus is used in the electrolysis of water?
Voltmeter
Voltameter
Ammeter
Potentiometer
Which of the following rays has the highest penetrative power?
a -rays
� -rays
? -rays
X-rays
A solid ball of metal has a spherical cavity inside it. When the ball is heated the volume of the cavity will
increase
decrease
remain unaffected
have its shape changed
The device used to record the sound is
a microphone
a headphone
a phonograph
an amplifier
The neutron, one of the constituent particles of which the nuclei of atoms are composed was discovered by
Irene Curie
W Bothe and H Becker
James Chadwick
Jean Joliot
Ultrasonic waves are used
in medical and surgical diagnosis
in testing the quality of the linings and pads used in vehicles and aircraft brakes
to clean surgical instruments, jewellery and similar articles
All the above
The inside of both the walls of a thermos flask is silvered i.e., on the vacuum side in order to reduce heat loss by
convection
radiation
conduction
All the three
The velocity required to place a vehicle in orbit round the moon is _________ that required to place it in orbit round the earth.
less than
greater than
equal to
greater than or equal to
A thermostat is a device used
for automatically maintaining a steady temperature
for measuring electricity
to reduce the voltage of electricity
for producing heat
At temperature near OK, (zero kelvin) metals such as lead and tin become
insulators
semiconductors
superconductors
condenser
A person cups his hand around the mouth when shouting. Why?
Sound energy from his mouth is then directed in one direction
The cupped hand acts as a cardboard tube of short length
The pitch of sound increases
Both (a) and (b)
A wire conveying a current deflects a pivoted magnetic needle. This was discovered by
Marconi
Oersted
Faraday
Ohm
Enriched uranium means
Uranium that is very pure
Uranium in which the concentration of the isotope U-238 is more than in the naturally occuring uranium
Uranium in which the concentration of the isotope U-235 is more than in the naturally occuring uranium
None of the above
The extremely luminous objects located at the centre of some distant galaxies and which are sources of high energy electromagnetic radiation are known as
Nebulae
Quasars
Meteors
Comets
The largest planet in the solar system is
Neptune
Uranus
Jupiter
Saturn
The planet that is known as earth's twin is
Mercury
Venus
Moon
Mars
The characteristics of a musical note are
loudness
pitch
quality or timbre
All the above
The strength of an electromagnet can be increased by
increasing the length of the coiled wire
increasing current supply
increasing the size of the iron core
All the above