Ultravoilet Rays

Q.

What is one important function of Fluorescent screen?

Q. What is the wavelength (in nm) of the spectral line associated with a tradition from n=3 to n=2 for Li2+ion (R= 109677)

Q.

Which among the following is the source of ultraviolet rays?

1. Red hot ion ball

2. Electric bulb

3. Carbon - arc lamp

4. Sodium vapour lamp

Q.

If the magnetic field in a plane electromagnetic wave is given by $\mathrm{B}=3\times {10}^{-8}\sin (1.6\times {10}^3\mathrm{x}+48\times {10}^{10}\mathrm{t})\hat{\mathrm{j}}$ $\mathrm{T}$ then what will be the expression for the electric field?

1. $\mathrm{E}=3\times {10}^{-8}\sin (1.6\times {10}^3\mathrm{x}+48\times {10}^{10}\mathrm{t})\hat{\mathrm{i}}\mathrm{V}{\mathrm{m}}^{-1}$

2. $\mathrm{E}=3\times {10}^{-8}\sin (1.6\times {10}^3\mathrm{x}+48\times {10}^{10}\mathrm{t})\hat{\mathrm{j}}\mathrm{V}{\mathrm{m}}^{-1}$

3. $\mathrm{E}=60\sin (1.6\times {10}^3\mathrm{x}+48\times {10}^{10}\mathrm{t})\hat{\mathrm{k}}\mathrm{V}{\mathrm{m}}^{-1}$

4. $\mathrm{E}=9\sin (1.6\times {10}^3\mathrm{x}+48\times {10}^{10}\mathrm{t})\hat{\mathrm{k}}\mathrm{V}{\mathrm{m}}^{-1}$

Q.

Who invented the tube light?

Q.

Give one use each of (a) microwaves , (b) ultraviolet radiations , (c) infrared radiations, and (d) gamma rays.

Q.

What is the main source of UV rays?

1. Lightning

2. Sun

3. Fluorescent lamp

4. Nuclear reactor

Q.

Which of the following are the properties of ultraviolet radiations?

1. They have wavelength in the range of 10 nm to 400 nm.

2. They cause fluorescence on Zinc sulphite screen.

3. They are invisible to human eyes.

4. They have wavelength in the range of 100 nm to 200 nm.

Q.

The source of ultraviolet light is :

(a) electric bulb (b) red hot iron ball

(c) sodium vapour lamp (d) Carbon arc - lamp.

Q.

Give reason for the following :

(i) Infrared radiations are used for photography in fog.

(ii) Infrared radiations are used for signals during the war.

(iii) The photographic darkrooms are provided with the infrared lamps.

(iv) A rock salt prism is used instead of a glass prism to obtain the infrared spectrum.

(v) A quartz prism is required for obtaining the spectrum of the ultraviolet light.

(vi) Ultraviolet bulbs have a quartz envelope instead of glass.

Q. (i) Name the system which enables us to locate underwater objects by transmitting ultrasonic waves and detecting the reflecting impulse.

(ii) What are acoustically measurable quantities related to pitch and loudness?

Q.

What are ultraviolet radiations ? How are they detected ? State one use of these radiations.

Q.

Name three radiations and their wavelength range which are invisible and beyond the violet end of the visible spectrum.

Q.

Name two electromagnetic waves of wavelength smaller than that of violet light. State one use of each.

Q.

State the approximate range of wavelength associated with (a) the ultraviolet rays , (b) the visible light , and (c) infrared rays.

Q.

If the magnetic field of a plane electromagnetic wave is given by (The speed of light =$3\times {10}^8\mathrm{m}{\mathrm{s}}^{-1}$)

$\mathrm{B}=100\times {10}^{-6}\sin \left(2\mathrm{\pi }\times 2\times {10}^{15}\left(\mathrm{t}-\frac{\mathrm{x}}{\mathrm{c}}\right)\right)$then the maximum electric field associated with it is

1. $4\times {10}^4{\mathrm{NC}}^{-1}$

2. $6\times {10}^4{\mathrm{NC}}^{-1}$

3. $3\times {10}^4{\mathrm{NC}}^{-1}$

4. $4.5\times {10}^4{\mathrm{NC}}^{-1}$

Q. Ultrasonic waves are used for manufacturing emulsion for photographic films because___

1. two immiscible liquids can be homogenised by using ultrasonic waves.
2. two immiscible liquids cannot be homogenised by using ultrasonic waves.
3. two miscible liquids can be separated by using ultrasonic waves.
4. None of these

Q. The magnetic field in a plane electromagnetic wave is given by $=2\times {10}^{-7}\sin (0.5\times {10}^{3}x+1.5\times {10}^{11}t)$. This electromagnetic wave is

1. Visible light
2. Infrared
3. Microwave
4. Radiowave

Q.

Give two properties of ultraviolet radiations which differ from the visible light.

Q. Skin cancer is caused by ___ rays.

1. IR
2. X
3. UV
4. visible

Q.

Name the radiations:

that are used for the detection of fractures in bones.

Q.

One source of background radiation is

1. Radiations from surrounding planets

2. Plastic wastes that human beings generate

3. Sewage

4. Radioelements like C¹⁴ and K⁴⁰ present in human beings

Q.

Which of the following have zero average value in a plane electromagnetic wave?

1. Electric energy

2. Magnetic energy

3. Electric field

4. Both magnetic and electric field

Q. Fluorescent tubes give more light than a filament bulb of same power because

1. the tube contains gas at low temperature
2. ultraviolet light is converted into visible light by fluorescence
3. it produces more heat than bulb
4. light is diffused through the walls of the tube

Q.

Name the radiations of wavelength just (a) longer than $8\times {10}^{-7}m,$ (b) shorter than $4\times {10}^{-7}m$.

Q. Name the prism required for obtaining the spectrum of infra red radiation

1. water
2. glass
3. rock salt prism
4. quartz prism

Q. Give one use of ultraviolet radiations.

Q.

Which of the following is true for electromagnetic radiations?

1. Do not follow laws of reflection/ refraction and are not deflected by electric and magnetic fields.

2. Travel at the same speed in a vacuum and are deflected by electric and magnetic fields.

3. Follow laws of reflection/refraction are not deflected by electric and magnetic fields.

4. Travel at different speeds in all media and follow laws of reflection/refraction.

Q. Welders wear special goggles or face masks with glass windows to protect their eyes from electromagnetic radiations. Names the radiations and write the range of their frequency

Q. Which of the following is not one of the prime health risks associated with greater UV radiation due to the depletion of stratospheric ozone?

1. Increased liver cancer.
2. Reduced immune system
3. Damage to eyes.
4. Increased skin cancer.