Atoms — Physics STD 12 Science — Question

The mass number of He is 4 and that for sulphur is 32. The radius of sulphur nucleus is larger than that of helium, by times

(a)

(b) 4

(c) 2

(d) 8

In which radioactive disintegration, neutron dissociates into proton and electron

(a)  emission

(b) β - emission

(c) γ - emission

(d) Positron emission

A uniform wire of resistance 9 W is cut into 3 equal parts.  They are connected in the form of equilateral triangle ABC.  A cell of e.m.f. 2 V and negligible internal resistance is connected across B and C.  Potential difference across AB is

(a) 1 V

(b) 2 V

(c) 3 V

(d) 0.5 V

Why are alkali metals most suited as photo-sensitive metals?

Calculate the de-Brogile wavelength of an electron travelling at 1% of the speed of light:

Wave front formed by the collimator of a spectrometer:

Wavelength of light of frequency 100Hz

(a) 2

(b) 3

(c) 4

(d) 5

The dielectric strength of air at NTP is 3  then the maximum charge that can be given to a spherical conductor of radius 3 m is

(a) 3

(b) 3

(c) 3

(d) 3

Each atom of an iron bar (5cm × 1 cm × 1 cm)  has a magnetic moment 1.8 .  Knowing that the density of iron is 7.78  atomic weight is 56 and Avogadro's  number is 6.02   the magnetic moment of bar in the state of magnetic saturation will be

(a) 4.75

(b) 5.74

(c) 7.54

(d)  75.4

The wavelength of maximum energy, released during an atomic explosion, was 2.93 × 10^–10 m. Given that the Wien's constant is 2.93 × 10^–3 m K, the maximum temperature attained must be of the order of

(a) 10–7 K

(b) 107 K

(c) 10–13 K

(d) 5.86 × 107 K