If λ1 and λ2 are the wavelengths of the first members of the Lyman and Paschen series respectively, then λ1 : λ2 is
1 : 3
1 : 30
7 : 50
7 : 108
The activity of a radioactive sample decreases to
(1/3)rd of its original value in 3 days. Then, in 9 days its activity will become
(1/27) of the original value
(1/9) of the original value
(1/18) of the original value
(1/3) of the original value
The working of which of the following is similar to that of a slide projector?
Electron microscope
Scanning electron microscope
Transmission electron microscope
Atomic force microscope
In a transistor, the collector current is always less than the emitter current because
collector side is reverse biased and the emitter side is forward biased
a few electrons are lost in the base and only remaining ones reach the collector
collector being reverse biased attracts less electron
collector side is forward biased and emitter side is reverse biased
The specific rotation of a sugar solution is 0.5 deg m2/kg. 200 kg-m-3 of impure sugar solution is- taken in a sample polarimeter tube of length 20 cm and optical rotation is found to be 19°. The percentage of purity of sugar is
20%
80%
95%
89%
To a germanium crystal, an equal number of aluminium and indium atoms are added. Then
it remains an intrinsic semiconductor
it becomes a n-type semiconductor
it becomes a p-type semiconductor
it becomes an insulator
C.
it becomes a p-type semiconductor
If a trivalent impurity is mixed with pure germanium crystal, the crystal so obtained is called p-type semiconductor. Here, aluminium and indium atoms are trivalent impurity atoms.
Maximum velocity of the photoelectrons emitted by a metal surface is 1.2x106 ms-1. Assuming the specific charge of the electron to be 1.8 x1011 C kg-1, the value of the stopping potential in volt will be
2
3
4
6
Which of the following figures represents the variation of the particle momentum and associated de-Broglie wavelength?
If r1 and r2 are the radii of the atomic nuclei of mass numbers 64 and 125 respectively, then the ratio (r1/r2) is
64/125
5/4
4/5