Study And Develop a Better India: August 2013

Question 10.1:
Monochromatic light of wavelength 589 nm is incident from air on a water surface. What are the wavelength, frequency and speed of (a) reflected, and (b) refracted light?
Refractive index of water is 1.33.

NCERT Solutions for Class 12th Physics Chapter 2 - Electrostatic Potential And Capacitance

Class 12th Physics Chapter 2 - Electrostatic Potential And Capacitance Solutions

NCERT Solutions for Class 12th Physics Chapter 15 - Communication Systems

NCERT Solutions for Class 12th Physics Chapter 15 - Communication Systems

Question 15.1:
Which of the following frequencies will be suitable for beyond-the-horizon communication
using sky waves?
(a) 10 kHz
(b) 10 MHz
(c) 1 GHz
(d) 1000 GHz
Answer
(b) Answer:
10 MHz
For beyond-the-horizon communication, it is necessary for the signal waves to travel a large distance. 10 KHz signals cannot be radiated efficiently because of the antenna size.
The high energy signal waves (1GHz − 1000 GHz) penetrate the ionosphere. 10 MHz frequencies get reflected easily from the ionosphere. Hence, signal waves of such frequencies are suitable for beyond-the-horizon communication.
Question 15.2:
Frequencies in the UHF range normally propagate by means of:
(a) Ground waves.
(b) Sky waves.
(c) Surface waves.
(d) Space waves.

NCERT Solutions for Class 12th Physics Chapter 14 - Semiconductor Electronics Materials Devices And Simple Circuits

NCERT Solutions for Class 12th Physics Chapter 14 - Semiconductor Electronics Materials Devices And Simple Circuits

Question 14.1:
In an n-type silicon, which of the following statement is true:
(a) Electrons are majority carriers and trivalent atoms are the dopants.
(b) Electrons are minority carriers and pentavalent atoms are the dopants.
(c) Holes are minority carriers and pentavalent atoms are the dopants.
(d) Holes are majority carriers and trivalent atoms are the dopants.
Answer
The correct statement is (c).
In an n-type silicon, the electrons are the majority carriers, while the holes are the minority carriers. An n-type semiconductor is obtained when pentavalent atoms, such as phosphorus, are doped in silicon atoms.
Question 14.2:
Which of the statements given in Exercise 14.1 is true for p-type semiconductors.
Answer
The correct statement is (d).

NCERT Solutions for Class 12th Physics Chapter 13 - Nuclei

NCERT Solutions for Class 12th Physics Chapter 13 - Nuclei

NCERT Solutions for Class 12th Physics Chapter 12 - Atoms

NCERT Solutions for Class 12th Physics Chapter 12 -

Atoms

Question 11.1:
Find the
(a) maximum frequency, and
(b) minimum wavelength of X-rays produced by 30 kV electrons.

NCERT Solutions for Class 12th Physics Chapter 9 - Ray Optics And Optical Instruments

NCERT Solutions for Class 12th Physics Chapter 9 - Ray Optics And Optical Instruments

Question 9.1:
A small candle, 2.5 cm in size is placed at 27 cm in front of a concave mirror of radius of curvature 36 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Describe the nature and size of the image.
If the candle is moved closer to the mirror, how would the screen have to be moved?
Answer
Size of the candle, h = 2.5 cm
Image size = h’
Object distance, u = −27 cm

NCERT Solutions for Class 12th Physics Chapter 8 - Electromagnetic Waves

NCERT Solutions for Class 12th Physics Chapter 8 - Electromagnetic Waves

Question 8.1: Figure 8.6 shows a capacitor made of two circular plates each of radius 12 cm, and separated by 5.0 cm. The capacitor is being charged by an external source (not shown in the figure). The charging current is constant and equal to 0.15 A.

(a) Calculate the capacitance and the rate of charge

NCERT Solutions for Class 12th Physics Chapter 7 - Alternating Current

NCERT Solutions for Class 12th Physics Chapter 7 - Alternating Current

NCERT Solutions for Class 12th Physics Chapter 6 - Electromagnetic Induction

NCERT Solutions for Class 12th Physics Chapter 6 - Electromagnetic Induction

NCERT Solutions for Class 12th Physics Chapter 5 - Magnetism And Matter

NCERT Solutions for Class 12th Physics Chapter 5 - Magnetism And Matter

Question5.1. Answer the following questions regarding earth’s magnetism:

(a) A vector needs three quantities for its specification. Name the three independent quantities conventionally used to specify the earth’s magnetic field.
(b) The angle of dip at a location in southern India is about 18º. Would you expect a greater or smaller dip angle in Britain?
(c) If you made a map of magnetic field lines at Melbourne in Australia, would the lines seem to go into the ground or come out of the ground?
(d) In which direction would a compass free to move in the vertical plane point to, if located right on the geomagnetic north or south pole?
(e) The earth’s field, it is claimed, roughly approximates the field due to a dipole of magnetic moment 8 × 1022 J T−1 located at its centre. Check the order of magnitude of this number in some way.
(f ) Geologists claim that besides the main magnetic N-S poles, there are several local poles on the earth’s surface oriented in different directions. How is such a thing possible at all?
Answer

NCERT Solutions for Class 12th Physics Chapter 4 - Moving Charges And Magnetism

NCERT Solutions for Class 12th Physics Chapter 4 - Moving Charges And Magnetism

NCERT Solutions for Class 12th Physics Chapter 3 - Current Electricity

NCERT Solutions for Class 12th Physics Chapter 3 - Current Electricity

Thursday, 22 August 2013

Tuesday, 20 August 2013

Saturday, 10 August 2013