Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

Download the PDF Sample Papers Free for off line practice and view the Solutions online.

ISC Class 12 Physics Solved Question Paper 2005

Short Answer Type

31. Define dispersive power of the material of a prism. The refractive indices of a prism for violet, yellow and red colours are 1.632,1.620 and 1.613 respectively. Calculate the dispersive power of the material of the prism.

Dispersive power :

The dispersive power of the material of a prism is defined as the ratio of angular dispersion between two extreme colours, to the deviation produced by the mean colour.

straight omega space equals space fraction numerator straight delta subscript straight v space minus space straight delta subscript straight R over denominator straight delta subscript straight Y end fraction

where,

δ_v = (μ _v - 1) A,

δ_R = (μ_R- 1) A

δ_y = (μ_y - 1) A,

μ_v = 1.632,

μ_R = 1.613,

μ_y = 1.620

This implies,

$straight omega space equals space fraction numerator straight mu subscript straight v space minus space straight mu over denominator straight mu subscript straight y space minus space 1 end fraction straight omega space equals space fraction numerator 0.019 over denominator 0.620 end fraction space equals space 0.030$

1361 Views

32. A convex lens and a plane mirror are kept at a distance of 10 cm as shown in the diagram. Parallel rays incident on the convex lens after reflection from the mirror form an image at the optical centre. Complete the ray diagram and find out the focal length of the lens.

360 Views

33. Explain why light waves can be polarised but sound waves cannot. Describe a method by which a plane polarised light can be distinguished from a partially polarised light.

469 Views

34. Sunglasses have curved surfaces, but their power is zero. Why ?

750 Views

35. Define magnifying power of an optical instrument. An astronomical refracting telescope consists of two lenses of focal length 75 cm and 5 cm. Calculate the magnifying power of the telescope when the final image is formed at a distance of 25 cm from the eye.

589 Views

36. What is Compton scattering ? Mention the important conclusion drawn from the phenomenon of Compton scattering.

1106 Views

37.

The threshold wavelength of tungsten is 2400 Å.

When tungsten is illuminated with light of wavelength 1600 Å, find :

(i) Work function

(ii) Maximum kinetic energy of the emitted electron

(iii) Stopping potential.

420 Views

38. In a Thomson set-up for finding e/m, the electrons are accelerated through a potential difference of 2500 V. The electrons then enter a region of crossed electric and magnetic fields of magnitudes 3.6 x 10⁴ V/m and 1.2 x 10 ³ T respectively and pass through undeviated. Calculate the e/m of an electron.

279 Views

39. In a hydrogen atom a transition of electrons take place from 3^rd orbit to 2^nd orbit. Calculate the wavelength of the emitted photon. To which spectral series will this photon belong ?

354 Views