51.

A galvanometer has a resistance of 4 Ω and a full scale deflection is produced by 12 mA current. What resistance must be connected in series with it to enable it to read 1.2 V ?

• 45 Ω

• 96 Ω

• 80 Ω

• 40 Ω

A beam of monochromatic light is incident on one face of an equilateral prism. The angle of incidence is 55°. If the angle of emergence is 46°, then the angle of minimum deviation ${\mathrm{\delta }}_{\mathrm{m}}$will be

• > 41°

• < 41°

• = 41°

• ≥ 41°

Mark the wrong statement regarding polarisation of light

• The vibrations in a plane polarised light are perpendicular to the plane of polarisation

• If a polarised light of intensity l₀ , is passed through an analyser the intensity of light transmitted is I = l₀ cos² θ

• Polarisation is the property of longitudinal wave

• Tangent of polarising angle is equal to the refractive index of medium upon which the light is incident

The blue colour of sky is explained by

• reflection

• scattering

• polarisation

• refraction

The wavelength of first Lyman series in the transition from n = 2 to n = 1 is

• 110 nm

• 120 nm

• 122 nm

• 125 nm

When a radioactive isotope ${}_{88}\mathrm{Ra}^{228}$ decay in series by the emission of 3$\mathrm{\alpha }$ -particles and a β -particle, the isotope finally formed is

• ${}_{82}\mathrm{X}^{216}$

• ${}_{83}\mathrm{X}^{215}$

• ${}_{88}\mathrm{X}^{216}$

• ${}_{83}\mathrm{X}^{216}$

λ₁, λ₂, λ₃ are de-Broglie wavelengths of electron, proton and $\mathrm{\alpha }$ - particle. If they are accelerated by same potential, then

• λ₁ < λ₂ < λ₃

• λ₁ >λ₂ > λ₃

• λ₁ < λ₂ > λ₃

• λ₁ > λ₂ < λ₃

A transistor is connected in CE configuration. The supply to the collector is 8 V and the voltage drop across a resistor of 400 Ω in the collector circuit is 0.5 V. If the current gain factor is $\mathrm{\alpha }$ = 0.96 then, the base current will be nearly

• 52 µA

• 42 µA

• 32 µA

• 26 µA

The width of depletion layer in a p-n junction diode

• increases when a forward bias is applied

• increases when a reverse bias is applied

• decreases when a reverse bias is applied

• remains same irrespective of bias voltage

Which of the following truth table is of NAND gate ?