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Physics Part-I
Class 12
NCERT
1
Chapter 1: Electric Charges and Fields
47 questions
2
Chapter 2: Electrostatic Potential and Capacitance
46 questions
3
Chapter 3: Current Electricity
33 questions
4
Chapter 4: Moving Charges and Magnetism
41 questions
5
Chapter 5: Magnetism and Matter
36 questions
6
Chapter 6: Electromagnetic Induction
28 questions
7
Chapter 7: Alternating Current
37 questions
8
Chapter 8: Electromagnetic Waves
20 questions
Q1
About 5% of the power of a 100 W light bulb is converted to visible radiation. What is the average intensity of visible radiation
(a) at a distance of 1m from the bulb?
(b) at a distance of 10 m?
Assume that the radiation is emitted isotropically and neglect reflection.
Q2
Use the formula T = 0.29 cm K to obtain the characteristic temperature ranges for different parts of the electromagnetic spectrum. What do the numbers that you obtain tell you?
Q3
Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. State the part of the electromagnetic spectrum to which each belongs.
(a) 21 cm (wavelength emitted by atomic hydrogen in interstellar space).
(b) 1057 MHz (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift).
(c) 2.7 K [temperature associated with the isotropic radiation filling all space thought to be a relic of the big-bang origin of the universe].
(d) [double lines of sodium]
(e) 14.4 ke V [energy of a particular transition in Fe nucleus associated with a famous high resolution spectroscopic method ()].
Question
Medium
Solving time: 4 mins
Use the formula T = 0.29 cm K to obtain the characteristic temperature ranges for different parts of the electromagnetic spectrum. What do the numbers that you obtain tell you?
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A body at temperature T produces a continuous spectrum of wavelengths. For a black body, the wavelength corresponding to maximum intensity of radiation is given according to Planck's law by the relation, . For .Temperatures for other wavelengths can be found. These numbers tell us the temperature ranges required for obtaining radiations in different parts of the electromagnetic spectrum. Thus, to obtain visible radiation, say , the source should have a temperature of about . A lower temperature will also produce this wavelength but not the maximum intensity.
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Practice more questions from Physics Part-I (NCERT)
Q1
About 5% of the power of a 100 W light bulb is converted to visible radiation. What is the average intensity of visible radiation
(a) at a distance of 1m from the bulb?
(b) at a distance of 10 m?
Assume that the radiation is emitted isotropically and neglect reflection.
Q2
Use the formula T = 0.29 cm K to obtain the characteristic temperature ranges for different parts of the electromagnetic spectrum. What do the numbers that you obtain tell you?
Q3
Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. State the part of the electromagnetic spectrum to which each belongs.
(a) 21 cm (wavelength emitted by atomic hydrogen in interstellar space).
(b) 1057 MHz (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift).
(c) 2.7 K [temperature associated with the isotropic radiation filling all space thought to be a relic of the big-bang origin of the universe].
(d) [double lines of sodium]
(e) 14.4 ke V [energy of a particular transition in Fe nucleus associated with a famous high resolution spectroscopic method ()].
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Assume that the radiation is emitted isotropically and neglect reflection.
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| Question Text | Use the formula T = 0.29 cm K to obtain the characteristic temperature ranges for different parts of the electromagnetic spectrum. What do the numbers that you obtain tell you? |
| Topic | Electromagnetic Waves |
| Subject | Physics |
| Class | Class 12 |
| Answer Type | Text solution:1 |
| Upvotes | 21 |
