Solid targets of different elements are bombarded by highly energetic electron beams. The frequency (f) of the characteristic X-rays emitted from different targets varies with atomic number Z as
f ∝
f ∝ Z2
f ∝ Z
f ∝ Z3/2
In a semiconductor material the mobilities of electrons and holes are μe and μn respectively. Which of the following is true?
μe > μn
μe < μn
μe = μn
μe< 0 ; μn > 0
The magnetic moment ( μ) of a revolving electron around the nucleus varies with principal quantum number n as
μ ∝ n
μ ∝ 1/n
μ ∝ n2
μ ∝ 1/n2
A radioactive material has a half-life of 10 days. What fraction of the material would remain after 30 days?
0.5
0.25
0.125
0.33
According to Hubble's law, the redshift (Z) of a receding galaxy and its distance r from earth are related as
Z ∝ r
Z ∝ 1/r
Z ∝ 1/r2
Z ∝ r3/2
When exposed to sunlight, thin films of oil on water often exhibit brilliant colours due to the phenomenon of
interference
diffraction
dispersion
polarisation
The apparent depth of water in cylindrical water tank of diameter 2R cm is reducing at the rate of x cm/minute when water is being drained out at a constant rate. The amount of water drained in c.c. per minute is ( n1 = refractive index of air, n2 = refractive index of water)
R2x
Assertion: Specific gravity of a fluid is a dimensionless quantity.
Reason: It is the ratio of density of fluid to the density of water.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
C.
If assertion is true but reason is false
When glass surface is made rough then the light falling on it is scattered in different direction due to which its transparency decreases. Due to rough surfaces light scatter more, so absorption of light is less.