# CBSE Delhi-Set-2-2010

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• Q1

Figure shows three point charges, +2q, -q and +3q. Two charges +2q and –q are enclosed within a surface ‘S’. What is the electric flux due to this configuration through the surface ‘S’?

Marks:1

• Q2

A glass lens of refractive index 1.45 disappears when immersed in a liquid. What is the value of refractive index of the liquid?

Marks:1

A glass lens will seem to disappear when immersed in a liquid only when the refractive indices of the glass lens and the liquid are same, as there will be no refraction of light. Therefore, the value of refractive index of the liquid is 1.45.

• Q3

In which orientation, a dipole placed in a uniform electric field is in (i) stable, (ii) unstable?

Marks:1

(i) The dipole is in stable equilibrium (W= – pE) when electric dipole moment is directed along the direction of the uniform electric field.
(ii) The dipole is in unstable equilibrium (W = pE) when the electric dipole moment is directed opposite to the direction of the uniform electric field.

• Q4

Which part of electromagnetic spectrum has largest penetrating power?

Marks:1

Gamma rays (frequency range 5 1022 to 3 1018 Hz) have the largest penetrating power.

• Q5

State the conditions for the phenomenon of total internal reflection to occur.

Marks:1

The conditions for the phenomenon of total internal reflection to occur are:
(i) Light rays should travel from a denser medium to a rarer medium.
(ii)  Angle of incidence (in the denser medium) should be greater than the critical angle for the pair of media in contact.

• Q6

A wire of resistance 8R is bent in the form of a circle. What is the effective resistance between the ends of a diameter AB?

Marks:1

Suppose R1 and R2 are resistances of semicircular parts of the wire and Re = Effective resistance betwe

• Q7

The radius of the innermost electron orbit of a hydrogen atom is 5.3  10-11 m. What is the radius of orbit in the second excited state?

Marks:1

• Q8

Which part of electromagnetic spectrum is absorbed from sunlight by ozone layer?

Marks:1

Ultraviolet rays are absorbed by ozone layer.

• Q9

Plot a graph showing the variation of stopping potential with the frequency of incident radiation for two different photosensitive materials having work functions W1 and W2 (W1 > W2). On what factors does the (i) slope and (ii) intercept of the lines depend?

Marks:2

The graph showing the variation of stopping potential with the frequency of incident radiation for two different photosensitive materials with different values of working functions is given below.

(i) The slope of the graph is content and equals to . Therefore, the slope does not depend on any factor.
(ii)  The intercept of the lines depends on the work function  of the metals

• Q10

(a) The bluish predominates in clear sky.
(b) Violet colour is seen at the bottom of the spectrum when white light is dispersed by a prism.

Marks:2