91. Which one of the following types of glass can cut of ultraviolet rays ?

1. 1. Soda glass

   
   
   

   2. Pyrex glass

   
   
   

   3. Jena glass

   
   
   

   4. Crookes glass

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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92. When a source of sound is in motion towards a stationary observer, the effect observed is

1. 1. Increase in the velocity of sound only

   
   
   

   2. Decrease in the velocity of sound only

   
   
   

   3. Increase in frequency of sound only

   
   
   

   4. Increase in both the velocity and the frequency sound

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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93. Which of the following is the infrared wavelength?

1. 1. 10^-4 cm

   
   
   

   2. 10^-5 cm

   
   
   

   3. 10^-6 cm

   
   
   

   4. 10^-7 cm

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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94. If V_1, V₂ and V₃ are the velocities of sound in steel, water and vacuum respectively, which one of the following relations is correct ?

1. 1. V₁ < V₂ < V₃

   
   
   

   2. V₁ < V₂ + V₃

   
   
   

   3. V₁ = V₂ = V₃

   
   
   

   4. V₁ . V₂ . V₃ = 0

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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95. Which of the following electromagnetic waves has the longest wavelength ?

1. 1. Infrared rays

   
   
   

   2. Gamma rays

   
   
   

   3. Light rays

   
   
   

   4. Ultraviolet rays

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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