Spectrum

Question 1

angle of deviation depends on

Answer 1

1. angle of incidence
2. angle of prism
3. refractive index of material of prism

Question 2

f of red light

Answer 2

3.75* 10^14 Hz

Question 3

f of violet light

Answer 3

7.5*10^14

Question 4

white light is ___________ in nature

Answer 4

polychromatic (consisting of seven prominent colours each corresponding to small wavelengths)

Question 5

define dispersion

Answer 5

the phenomenon of splitting of white light by a prism into its constituent colours is known as dispersion

Question 6

define spectrum

Answer 6

on passing white light through a prism, the band of colours seen on a screen is called the spectrum

Question 7

define invisible spectrum

Answer 7

the part of the spectrum beyond the red extreme and the violet extreme is called the invisible spectrum

Question 8

waves of wavelength longer than the red part of visible spectrum, in increasing order of wavelength

Answer 8

1. infrared radiations
2. microwaves
3. radio waves

Question 9

waves of wavelength shorter than violet of visible spectrum, in decreasing order of wavelength

Answer 9

1. UV rays
2. X rays
3. gamma rays

Question 10

wavelength of gamma rays

Answer 10

shorter than 0.01 nm
frequency above 10^19

Question 11

wavelength of X-rays

Answer 11

0.01-10 nm

Question 12

wavelength of UV rays

Answer 12

10 nm - 400 nm

Question 13

visible light wavelength

Answer 13

400 nm to 800 nm

Question 14

infrared radiations wavelength

Answer 14

800 nm to 1 mm

Question 15

microwaves wavelength

Answer 15

1 mm to 1 m

Question 16

radio waves wavelength

Answer 16

greater than 1 m

Question 17

properties common to all electromagnetic waves

Answer 17

1. do not require material medium for propagation
2. travel with same speed in vacuum and air, different speeds in different media
3. exhibits reflection and refraction (in refraction, wavelength, speed, direction changes but frequency does not)
4. waves are not deflected by electric and magnetic fields
5. waves are transverse in nature

Question 18

properties of gamma rays

Answer 18

1. cause fluorescence when they strike the fluorescent materials like zinc sulphide
2. easily penetrate through thick metallic sheets
3. pass through human bodies and damage

Question 19

uses of gamma rays

Answer 19

controlled manner in medical science to kill cancer cells
in industry, to check welding

Question 20

properties of X-rays

Answer 20

1. chemically more active than UV
2. strongly affect photographic plate
3. cause fluorescence in zinc sulphide
4. penetrate through human flesh, but stopped by bones

Question 21

uses of x rays

Answer 21

1. detection of fracture
2. CAT scan in medical science
3. studying atomic arrangement in crystals as well as complex molecules
4. detect concealed precious metals

Question 22

detection of UV rays (actinic rays)

Answer 22

1. when AgCl soln is exposed to it it starting from red to violet then beyond it, it is observed that from the red end to violet end, soln. remains unaffected. beyond violet, soln. first turns violet then becomes dark brown or black- this shows that there are radiations beyond violet extreme of visible part which are chemically more active than visible light
2. by their chemical activity on dyes and photographic plates

Question 23

how is spectrum of UV rays obtained

Answer 23

the spectrum is obtained by passing radiations through a quartz prism instead of a glass prism, because glass absorbs the radiations

Question 24

properties of UV rays

Answer 24

1. can pass through quartz, but are absorbed by glass
2. travel in straight line with speed of 3*10^8 m/s
3. scattered by dust
4. obey laws of reflection and refraction
5. strongly affect photographic plate as THEY ARE MORE CHEMICALLY ACTIVE THAN VISIBLE LIGHT
6. produce fluorescence

Question 25

uses of UV

Answer 25

1. sterilising air, surgical equipment, etc
2. detecting purity of gems, eggs, ghee
3. producing vit D in food of plants and animals

Question 26

uses of visible light

Answer 26

1. photography
2. photosynthesis
3. to see

Question 27

detection of infrared radiations

Answer 27

1. if a thermometer having its bulb blackened is moved from violet end to red end of the spectrum, a rise in temperature is seen. on moving beyond the red spectrum, a rapid rise is noticed (heating effect)
2. galvanometer connected to thermopile shows deflection when infrared radiations fall on thermopile
3. spectrum is obtained by using rock-salt prism because a rock-salt prism does not absorb, but glass does

Question 28

properties of infrared radiations

Answer 28

1. travel in straight lines with same speed in vacuum
2. obey laws of reflection and refraction
3. do not affect ordinary photographic films, but a specially treated film is affected by them
4. detected by heating property by used blackened bulb thermometer or thermopile
5. scattered less in atmosphere due to long wavelength
6. greenhouse gases absorb infrared and keep earth warm

Question 29

uses of infrared

Answer 29

1. therapeutic purposes by doctors
2. photography in night, in mist and fog, because they are not scattered due to long wavelength
3. lamps used in dark rooms for developing photographs as they provide visibility without affecting photographic film
4. signals during war
5. remote control

Question 30

why are IFR radiations used as signals during war

Answer 30

not visible
not absorbed much in medium

Question 31

uses of microwaves

Answer 31

1. satellite communication
2. analysis of atomic and molecular structures
3. cooking in microwave ovens
4. radar communications

Question 32

uses of radio waves

Answer 32

radar communication
radio and television transmission