21. The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is

1. 1. microwave, infrared, ultraviolet, gamma rays

   
   
   

   2. ​gamma rays, ultraviolet, infrared, micro-waves ​

   
   
   

   3. microwaves, gamma rays, infrared, ultraviolet ​

   
   
   

   4. ​infrared, microwave, ultraviolet, gamma rays

   
   
   

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1. View Hint View Answer Discuss in Forum

   The decreasing order of the wavelengths is as given below : ​microwave, infrared, ultraviolet, gamma rays.

   Correct Option: A

   The decreasing order of the wavelengths is as given below : ​microwave, infrared, ultraviolet, gamma rays.

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22. ​If λ_v, λ_x and λ_m represent the wavelengths of visible light, X–rays and microwaves respectively, then​​​

1. 1. ​λ_m > λ_x > λ_v

   
   
   

   2. λ_m > λ_v > λ_x

   
   
   

   3. ​λ_v > λ_x > λ_m ​

   
   
   

   4. ​λ_v > λ_m > λ_x

   
   
   

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1. View Hint View Answer Discuss in Forum

   We know
   

   E =	hc
   	λ

   
   

   E ∝	1
   	λ

   
   E_m < E_v < E_x
   ∴ λ_m > λ_v > λ_x

   Correct Option: B

   We know
   

   E =	hc
   	λ

   
   

   E ∝	1
   	λ

   
   E_m < E_v < E_x
   ∴ λ_m > λ_v > λ_x

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23. Which one of the following rays is not electromagnetic wave ?

1. 1. heat rays

   
   
   

   2. X-rays ​

   
   
   

   3. γ-rays ​

   
   
   

   4. ​β-rays

   
   
   

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1. View Hint View Answer Discuss in Forum

   β ray is not electromagnetic ray

   Correct Option: D

   β ray is not electromagnetic ray

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24. We consider the radiation emitted by the human body. Which of the following statements is true?

1. 1. the radiation emitted lies in the ultraviolet region and hence is not visible.​ ​

   
   
   

   2. the radiation emitted is in the infra-red region.

   
   
   

   3. ​the radiation is emitted only during the day.

   
   
   

   4. the radiation is emitted during the summers and absorbed during the winters.

   
   
   

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1. View Hint View Answer Discuss in Forum

   Depends on the magnitude of frequency

   Correct Option: B

   Depends on the magnitude of frequency

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25. Which of the following electromagnetic radiations has the least wavelength?​

1. 1. gamma rays ​

   
   
   

   2. infra-red

   
   
   

   3. ultraviolet ​

   
   
   

   4. ​X-rays

   
   
   

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1. View Hint View Answer Discuss in Forum

   Gamma ray has highest frequency and lowest wavelength.

   Correct Option: A

   Gamma ray has highest frequency and lowest wavelength.

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