Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12

# PUC Karnataka Science Class 12 - Department of Pre-University Education, Karnataka Question Bank Solutions for Physics

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A circular coil of cross-sectional area 200 cm2 and 20 turns is rotated about the vertical diameter with angular speed of 50 rad s−1 in a uniform magnetic field of magnitude 3.0 × 10−2T. Calculate the maximum value of the current in the coil.

[0.07] Electromagnetic Induction
Chapter: [0.07] Electromagnetic Induction
Concept: Electromagnetic Induction

Why should the objective of a telescope have large focal length and large aperture? Justify your answer.

[0.09] Ray Optics and Optical Instruments
Chapter: [0.09] Ray Optics and Optical Instruments
Concept: Optical Instruments > Telescope

Draw a ray diagram depicting the formation of the image by an astronomical telescope in normal adjustment.

[0.09] Ray Optics and Optical Instruments
Chapter: [0.09] Ray Optics and Optical Instruments
Concept: Optical Instruments > Telescope

You are given the following three lenses. Which two lenses will you use as an eyepiece and as an objective to construct an astronomical telescope ? Give reason

 Lenses Power (D) Aperture (cm) L1 3 8 L2 6 1 L3 10 1
[0.09] Ray Optics and Optical Instruments
Chapter: [0.09] Ray Optics and Optical Instruments
Concept: Optical Instruments > Telescope

Show diagrammatically how an alternating emf is generated by a loop of wire rotating in a magnetic field. Write the expression for the instantaneous value of the emf induced in the rotating loop.

[0.07] Electromagnetic Induction
Chapter: [0.07] Electromagnetic Induction
Concept: Electromagnetic Induction

Is the colour of 620 nm light and 780 nm light same? Is the colour of 620 nm light and 621 nm light same? How many colours are there in white light?

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

The wavelength of light in a medium is $\lambda = \lambda_0 /\mu,$ where $\lambda$ is the wavelength in vacuum. A beam of red light $\left( \lambda_0 = 720\text{ nm} \right)$ enters water. The wavelength in water is $\lambda = \lambda_0 /\mu = 540\text{ nm.}$ To a person under water, does this light appear green?

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

If we put a cardboard (say 20 cm × 20 cm) between a light source and our eyes, we can't see the light. But when we put the same cardboard between a sound source and out ear, we hear the sound almost clearly. Explain.

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

TV signals broadcast by a Delhi studio cannot be directly received at Patna, which is about 1000 km away. But the same signal goes some 36000 km away to a satellite, gets reflected and is then received at Patna. Explain.

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

Is it necessary to have two waves of equal intensity to study interference pattern? Will there be an effect on clarity if the waves have unequal intensity?

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

Light is _______________ .

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

The speed of light depends ____________ .

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

The equation of a light wave is written as $y = A \sin\left( kx - \omega t \right).$ Here, y represents _______ .

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

An amplitude modulated (AM) radio wave bends appreciably round the corners of a 1 m × 1 m board but a frequency modulated (FM) wave only bends negligibly. If the average wavelengths of the AM and FM waves are $\lambda_a and \lambda_f,$

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

The inverse square law of intensity $\left(\text{i.e. the intensity }\infty \frac{1}{r^2}\right)$ is valid for a ____________ .

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

A light wave can travel

(a) in vacuum

(b) in vacuum only

(c) in a material medium

(d) in a material medium only

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

Which of the following properties of light conclusively support the wave theory of light?

(a) Light obeys the laws of reflection.

(b) Speed of light in water is smaller than its speed in vacuum.

(c) Light shows interference.

(d) Light shows photoelectric effect.

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

When light propagates in vacuum, there is an electric field as well as a magnetic field. These fields ____________ .

(a) are constant in time

(b) have zero average value

(c) are perpendicular to the direction of propagation of light.

(d) are mutually perpendicular

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

Three observers A, B and C measure the speed of light coming from a source to be νA, νBand νC. A moves towards the source and C moves away from the source at the same speed. B remains stationary. The surrounding space is vacuum everywhere.

(a) $\nu_A > \nu_B > \nu_C$

(b) $\nu_A < \nu_B < \nu_C$

(c) $\nu_A = \nu_B = \nu_C$

(d) $\nu_B = \frac{1}{2}\left( \nu_A + \nu_C \right)$

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

Three observers A, B and C measure the speed of light coming from a source to be νA, νBand νC. A moves towards the source and C moves away from the source at the same speed. B remains stationary. The surrounding space is water everywhere.

(a) $\nu_A > \nu_B > \nu_C$

(b) $\nu_A < \nu_B < \nu_C$

(c) $\nu_A = \nu_B = \nu_C$

(d) $\nu_B = \frac{1}{2}\left( \nu_A + \nu_C \right)$

[0.1] Wave Optics
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics
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