An α -particle of energy 5 MeV is scattered through 180° by gold nucleus. The distance of closest approach is of the order of
10-14 cm
10-10 cm
10-16 cm
10-12 cm
Find the de-Broglie wavelength of an electron with kinetic energy of 120 eV.
112 pm
95 pm
124 pm
102 pm
Light of two different frequencies whose photons have energies 1 eV and 2.5 eV respectively, successively illuminate a metallic surface whose work function is 0.5 eV. Ratio of maximum speeds of emitted electrons will be
1 : 2
1 : 5
1 : 1
1 : 4
The polarising angle of glass is 57°. A ray of light which is incident at this angle will have an angle of refraction as
43°
25°
38°
33°
D.
33°
Given, θP = 57°
According to Brewster's law, we have
θP + r = 90° ⇒ r = 90° − θP
r = 90° − 57
Angle of refraction, r = 33°
To observed diffraction, the size of the obstacle
should be much larger than the wavelength
has no relation to wavelength
should be of the order of wavelength
should be where λ is the wavelength
A radioactive decay can form an isotope of the original nucleus with the emission of particles
one α and one β
one α and four β
four α and one β
one α and two β
The half-life of a radioactive substance is 20 min. The time taken between 50 % decay and 87.5 % decay of the substance will be
25 min
30 min
10 min
40 min
A nucleus at rest splits into two nuclear parts having radii in the ratio 1 : 2. Their velocities are in the ratio
4 : 1
8 : 1
2 : 1
6 : 1
What is the wavelength of light for the least energetic photon emitted in the Lyman series of the hydrogen spectrum ? (take, hc = 1240 eV nm)
122 nm
82 nm
150 nm
102 nm
If an electron in hydrogen atom jumps from an orbit of level n = 3 to an orbit oflevel n =2, the emitted radiation has a frequency (R = Rydberg constant, c = velocity of light)