A diver in a swimming pool wants to signal his distress to a person lying on the edge of the pool by flashing his water proof flash light [NCERT 1972]

• A. He must direct the beam vertically upwards
• B. He has to direct the beam horizontally
• C. He has to direct the beam at an angle to the vertical which is slightly less than the critical angle of incidence for total internal reflection
• D. He has to direct the beam at an angle to the vertical which is slightly more than the critical angle of incidence for the total internal reflection