Q. 1. You are listening a soft music with a sound level of 50 dB. A subway train passes by whose sound level is 90 dB. What is the total intensity level of the combined sound in dB.

2. What is the air temperature if the speed of sound is a) 432 m/s b) 380 m/s

3. Compare the speed of sound in glass and granite. Which material can be best used to control sound?
Y glass = 70 N/m2 ρ glass = 2600 kg/m3
Y granite = 45 n/m2 ρ granite = 2700 kg/m3

4. Is the speed of light greater in ethyl alcohol or glycerine
n ethyl alcohol = 1.36 n glycerine = 1.47

5. A beam of light enters water at an angle of 60 0 angle of incidence. Find the angle of refraction.
n air = 1 n water = 1.33

6. Light passes from air into water. If the angle of refraction is 20 0, what is the angle of incidence.