Previous Year Paper year:2019 : ICSE-X-Physics

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ICSE-X-Physics

Previous Year Paper year:2019

with Solutions - page 5

#6

#6-a
How does the angle of deviation formed by a prism change with the increase in the angle of

incidence? Draw a graph showing the variation in the angle of deviation with the angle of incidence at a prism surface.

[3]

Ans : As the. angle of incidence increases the angle of deviation decreases becomes minimum and then increases.

The graph is as shown :

#6-b
A virtual, diminished image is formed when an object is placed between the optical centre and the principal focus of a lens.

#6-b-i
Name the type of lens which forms the above image.
Ans : Concave lens.

#6-b-ii
Draw a ray diagram to show the formation of the image with the above stated characteristics.

[3]

Ans : The ray diagram is as shown :

#6-c
An object is placed at a distance 24 cm in front of a convex lens of focal length 8 cm.
Ans : Given u = - 24 cm, f= + 8 cm, v = ?

#6-c-i
What is the nature of the image so formed ?
Ans : Real, inverted and diminished.

#6-c-ii
Calculate the distance of the image from the lens.
Ans : Using the lens formula

``\frac { v }{ u }`` = ``\frac { 12 }{ -24 }`` = ``\frac { 1 }{ 2 }`` .

#6-c-iii
Calculate the magnification of the image.

[4]

#7

#7-a
It is observed that during march-past we hear a base drum distinctly from a distance compared to the side drums.

#7-a-i
Name the characteristic of sound associated with the above observation.
Ans : Intensity of sound.

#7-a-ii
Give a reason for the above observation.

[3]

Ans : This is because the amplitude of vibration of a base drum is far greater than the amplitude of vibration of the side drum.

(b) Given f= 4 vbs, T = ``\frac { 1 }{ f }`` = ``\frac { 1 }{ 4 }`` = 0.25 s, for a frequency of 6 vbs titme t= ``\frac { 0.25 }{ 4 }`` x 6 = 0.375 s, ,V=340ms^-1

Using S = ``\frac{\mathbf{V} \times t}{2}`` = ``\frac{340 \times 0.375}{2}`` = 63.75 m

(c) (i) Free or natural oscillation.

(ii) Forced oscillation.

(iii) The amplitude of the oscillation of D will be equal to the amplitude of the oscillation of C.

(iv) Resonance.

#7-b
A pendulum has a frequency of 4 vibrations per second. An observer starts the pendulum and fires a gun simultaneously. He hears the echo from the cliff after 6 vibrations of the pendulum. If the velocity of sound in air is 340 m s1, find the distance between the cliff and the observer.

[3]

#7-c
Two pendulums C and D are suspended from a wire as shown in the given figure. Pendulum C is made to oscillate by displacing it from its mean position. It is seen that D also starts oscillating.