Assertion: Magnetic Resonance Imaging (MRI) is a useful diagnostic tool for producing images of various parts of human body.
Reason: Protons of various tissues of human body play a role in MRI.
If both assertion and reason are true and reason is the correct explanation of the assertion
If both assertion and reason are true but reason is not the correct explanation of the assertion
If assertion is true, but reason is false
Both assertion and reason are false statements
Assertion: Diamagnetic materials can exhibit magnetism.
Reason: Diamagnetic materials have permanent magnetic dipole moment.
If both assertion and reason are true and reason is the correct explanation of the assertion
If both assertion and reason are true but reason is not the correct explanation of the assertion
If assertion is true, but reason is false
Both assertion and reason are false statements.
D.
Both assertion and reason are false statements.
Some materials when placed in an external magnetic field, acquire a very low magnetism in a direction opposite to the field. These materials when brought near the end of a strong magnet, they get repelled. These materials are diamagnetic and this property of materials is called diamagnetism. This property is generally found in materials in which there are even number of electrons in their atoms ( or molecules ) and pairs are formed with two electrons. In each pair, the spin of one electron is in direction opposite to the spin of other electron. Hence, the electrons of each pair completely cancel the magnetic moment of each other. Thus, the net magnetic moment of each atom of such material is zero. Hence, option (c) is true.
Assertion: An emf is induced in a closed loop where magnetic flux is varied. The induced E is not a conservative field.
Reason: The line integral around the closed loop is non-zero.
If both assertion and reason are true and reason is the correct explanation of the assertion
If both assertion and reason are true but reason is not the correct explanation of the assertion
If assertion is true, but reason is false
Both assertion and reason are false statements
In refraction, light waves are bent on passing from one medium to the second medium, because in the second medium
the frequency is different
the coefficient of elasticity is different
the speed is different
the amplitude is smaller
A wire mesh consisting of very small squares is viewed at a distance of 8 cm through a magnifying converging lens of focal length 1O cm, kept close to the eye. The magnification produced by the lens is
5
8
10
20
Hard X - rays for the study of fractures in bones should have a minimum wavelength of 10-11 m. The accelerating voltage for electrons in X-ray machine should be
< 124.2 kV
> 124.2 kV
between 60 kV and 70 kV
= 100 kV
In photoelectric effect, the electrons are ejected from metals if the incident light has a certain minimum
wavelength
frequency
amplitude
angle of incidence
A lens is made of flint glass (refractive index= 1.5). When the lens is immersed in a liquid of refractive index 1.25, the focal length
increases by a factor of 1.25
increases by a factor of 2.5
increases by a factor of 1.2
decreases by a factor of 1.2
When a p-n diode is reverse biased,then
no current flows
the depletion region is increased
the depletion region is reduced
the height of the potential barrier is reduced
The operation of a nuclear reactor is said to be critical, if the multiplication factor ( K ) has a value
1
1.5
2.1
2.5