Tag: physics

Questions Related to physics

The heat in solar radiation is mainly due to the presence of _______ .

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. infrared radiations

  2. ultraviolet radiations

  3. visible light

  4. x-rays

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Correct Option: A

_________ are useful in studying the structures of crystals. 

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. All electromagnetic radiations

  2. Light rays

  3. X-rays

  4. $\gamma$-rays

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Correct Option: C
Explanation:

X-rays are useful in studying the structures of crystals

Why does radio reception improve slightly during the night ? 

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. The outside noise is reduced very much at night.

  2. Unlike the daytime, only a few radio stations broadcast during the night.

  3. Sunlight affects radio broadcasts to some extent during the day.

  4. The magnetic field of the earth acts with reduced intensity during the night, thereby reducing its impact on broadcasts.

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Correct Option: C
Explanation:

Answer is C.

The D region is the lowest of the regions within the ionosphere that affects radio communications signals to any degree. It is present at altitudes between about 60 and 90 kilometers and the radiation within it is only present during the day to an extent that affects radio waves noticeably. It is sustained by the radiation from the Sun and levels of ionization fall rapidly at dusk when the source of radiation is removed. It mainly has the affect of absorbing or attenuating radio communications signals particularly in the LF and MF portions of the radio spectrum, its affect reducing with frequency. At night it has little effect on most radio communications signals although there is still a sufficient level of ionization for it to refract VLF signals.
Hence, radio reception improve slightly during the night because, sunlight affects radio broadcasts to some extent during the day.

When an object absorb waves  and  energy their temperature increases.

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. True

  2. False

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Correct Option: A

Infrared radiation was discovered in $1800$ by.

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. William Wollaston

  2. William Herschel

  3. Wilhelm Roentgen

  4. Thomas Young

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Correct Option: B
Explanation:

Infrared radiation was discovered in $1800$ by $William Herschel$.

They discovered $\longrightarrow $ When sunlight went through various color filters; it produces different amount of heat. He hypothesized that colors could have different temperatures. He then passed light through glass prism, creating a color spectrum and analysing each color's temperature. He used three special thermometers.
For each color, one was placed within its bounds while the other two were outside as controls. The thermometer in the color had higher temperature than the others, and he found that each color going from violet to red was warmer than the last. He then placed a thermometer next to red light, where no color from spectrum were visible. He noticed that area had even higher temperature than color sections. He demonstrated that this visible type of light refracted and reflected the same way sunlight did.This light came to be known as infrared radiation.

Of the following waves has the longest wavelength?

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. X-rays

  2. Green light

  3. Orange light

  4. Microwaves

  5. Gamma rays

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Correct Option: D
Explanation:

Order of wavelength from shortest to longest :      

 Gamma rays < X-rays < Green light < Orange light < Microwaves 
Thus Microwaves has the longest wavelength.

State whether true or false :

Ultraviolet rays are used to take photographs in darkness.

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. True

  2. False

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Correct Option: B
Explanation:

Wrong

Infrared is used in dark for photography. All body emit infrared radiation every time.
Since infrared radiation is invisible, photography in total darkness can be readily carried out if infrared film is used and the light source is covered with a light-absorbing but infrared-transmitting filter.

The part of the electromagnetic spectrum which is suitable for radar systems used in aircraft navigation :

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. X-Rays

  2. Gamma Rays

  3. Microwaves or short radiowaves 

  4. Ultraviolet

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Correct Option: C
Explanation:

Microwaves or short radiowaves are suitable for radar systems used in aircraft navigation because of their short wavelengths.

 Which one of waves tans our skin and causes some substances to become fluorescent?

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. infrared waves.

  2. ultraviolet waves.

  3. gamma rays.

  4. infrared and ultraviolet waves both.

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Correct Option: B
Explanation:

Ultraviolet rays (or waves) tan our skin and cause some substances to become fluoroseun sun is important source of ultraviolet light. Sun rays reach our skin and burns the upper layer of skin, causing sunburns prolonged doses of UV radiation can induce skin cancer in human beings.

Ozone layer is protecting us from UV rays but the problem is that Ozone layer is also depleting because of excessive use of CFC's.

In photocell cesium, coated oxidized silver cathode emits electrons for

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. visible light.

  2. ultraviolet.

  3. infrared light.

  4. x-rays.

Show answer
Correct Option: C
Explanation:

In photocell cesium, coated oxidised silver cathode emits electrons for infrared light.