CBSE Delhi-Set-1-2010
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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:1View AnswerAnswer:
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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:1View AnswerAnswer:
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.
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Q3
A plot of magnetic flux (
Marks:1View AnswerAnswer:
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Q4
In which orientation, a dipole placed in a uniform electric field is in (i) stable, (ii) unstable?
Marks:1View AnswerAnswer:
(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. -
Q5
Which part of electromagnetic spectrum has largest penetrating power?
Marks:1View AnswerAnswer:
Gamma rays (frequency range 5
1018 Hz) have the largest penetrating power. -
Q6
State the conditions for the phenomenon of total internal reflection to occur.
Marks:1View AnswerAnswer:
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. -
Q7
What is the ratio of radii of the orbits corresponding to the first excited state and ground state in a hydrogen atom?
Marks:1View AnswerAnswer:
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Q8
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:1View AnswerAnswer:
Suppose R1 and R2 are resistances of semicircular parts of the wire and Re = Effective resistance betwe
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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:2View AnswerAnswer:
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:2View AnswerAnswer:
(a) The predominance of the blue colour in the sky is due to the scattering of light. As light moves through the atmosphere, most of the longer wavelength colours are able to pass straight through, whereas the shorter wavelength colours are absorbed by the gas molecules. The absorbed blue light is then radiated and scattered in different direction making the sky to look blue.
(b) Violet rays have the least wavelength and the greatest frequency. Therefore, when a beam of white light strikes a prism, the refractive index of the prism is the greatest for violet rays compared to other rays. Hence, violet rays bend the most. So, violet colour is seen at the bottom of the spectrum.
