76. Whose experiments proved that the speed of light was always the same?

1. 1. James Clark Maxwell

   
   
   

   2. Michelson and Marley

   
   
   

   3. Miller and Stanley

   
   
   

   4. Werner Heisenberg

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: B

   N/A

---

77. Why is red light employed for danger signals ?

1. 1. Red colour is soothing to the eye

   
   
   

   2. Human eye is most sensitive to red colour

   
   
   

   3. Red light is scattered least

   
   
   

   4. Red light is scattered most

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: C

   N/A

---

---

78. Plane mirrors A and B are kept at angle 0 with respect to each other. Light falls on A is reflected then falls on B and is reflected. The emergent ray is oppsite to the incident direction. The angle 0 is equal to

1. 1. 30°

   
   
   

   2. 45°

   
   
   

   3. 60°

   
   
   

   4. 90°

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: D

   N/A

---

79. To observe diffraction, the size of the obstacles

1. 1. Should be of the same order as the wavelength

   
   
   

   2. Should be much larger than the wavelength

   
   
   

   3. Has no relation to wavelength

   
   
   

   4. Should be exactly half the wavelength

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: A

   N/A

---

---

80. In a cinema hall, the distance between the projector and the screen is increased by 2% Then the intensity of illumination of the screen is

1. 1. Decreased by 2%

   
   
   

   2. Decreased by 4%

   
   
   

   3. Increased by 2%

   
   
   

   4. Increased by 4%

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: B

   N/A

---