CBSE Delhi-Set-3-2009
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Q1
Differentiate between a ray and a wave front.
Marks:1View AnswerAnswer:
Wave front is defined as the locus of all particles oscillating in the same phase during propagation of waves in a material medium. While a straight line drawn perpendicular to wave front gives the direction of propagation of wave and is known as a ray.
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Q2
The figure shows a plot of three curves a, b, c showing the variation of photocurrent vs collector plate potential for three different intensities I1, I2 and I3 having frequencies
respectively incident on a photosensitive surface.
Point out the two curves for which the incident radiations have same frequency but different intensities.
Marks:1View AnswerAnswer:
Curve a, b represents same frequency. The value of stopping potential is same for radiations having same frequency and is independent of the intensity of the incident radiation. Thus, a and b are the two curves for which the incident radiations have same frequency but different intensities.
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Q3
At what angle of incidence should a light beam strike a glass slab of refractive index (3)1/2 . Such that the reflected and the refracted rays are perpendicular to each other?
Marks:1View AnswerAnswer:
r + 900 + c0 = 1800 (linear pair)
c0 = 900 – r….(i)
i + r = 900
i = 900 – r
Sin i= Sin (900 – r)
Sin i = Cos r….. (2) (As sin(900-
) = cos
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Q4
What is space wave propagation?
Marks:1View AnswerAnswer:
When the radio waves from the transmitting antenna reach the receiving antenna either directly, or after reflection from the earth’s surface (or in troposphere) then, the wave propagation is known as ‘space wave propagation’.
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Q5
Name the part of electromagnetic spectrum which is suitable for
(i) radar systems used in aircraft navigation
(ii) treatment of cancer tumoursMarks:1View AnswerAnswer:
(i) Microwaves.
(ii) X-rays. -
Q6
You are given following three lenses. Which two lenses will you use as an eyepiece and as an objective to construct an astronomical telescope?
Lenses
Power (P)
Aperture (A)
L1
3D
8 cm
L2
6D
1 cm
L3
10D
1 cm
Marks:1View AnswerAnswer:
Focal length of eyepiece should be smaller than that of objective.
So, power of eyepiece should be greater as compared to an objective.L1
3 D
8 cm
Objective
L3
10D
1 cm
Eye piece
We will use L1 lens as an objective and L3 lens as an eyepiece to construct the astronomical telescope.
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Q7
Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid. Why?
Marks:1View AnswerAnswer:
Magnetic field lines can be entirely confined within the core of toroid because field lines form closed loops, but in case of straight solenoid it is not possible as it will violate Ampere’s law.
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Q8
Two nuclei have mass numbers in the ratio 2 : 5. What is the ratio of their nuclear densities?
Marks:1View AnswerAnswer:
Density of nuclear matter= mass of nucleus / volume of nucleus
=(3m)/(4
R03) As m and R0 are constants, therefore density
is independent of the mass number of atoms of all elements.
So, nuclear density is same for all nuclei, therefore,1/2 =1 -
Q9
(i) Sketch the output waveform from an AND gate for the inputs A and B shown in the figure.
(ii)If the output of the above AND gate is fed to a NOT gate, name the gate of the combination so formed.
Marks:2View AnswerAnswer:
(i).
(ii). AND + NOT = NAND
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Q10
By what percentage will the transmission range of a TV tower be affected when the height of the tower is increased by 21%?
Marks:2View AnswerAnswer:
The distance covered by the TV tower of height h is given by:
