The period of a pendulum is given by

since Karachi is near sea level, g is larger than it is on Mt. Everest. That means the pendulum will have a larger period on Mt. Everest than it would in Karachi.
When light travels from a medium with higher refractive index to a medium with lower refractive index, there is a critical angle after which all the light is reflected (so, there is no refraction).
The value of this critical angle can be derived by Snell's law, and it is equal to

where n2 is the refractive index of the second medium and n1 is the refractive index of the first medium.
In our problem, n1=1.47 and n2=1.33, so the critical angle is
They can.
Surfers use waves to move themselves around.
Answer:
Let M1 = 8 kg and M2 = 34 kg
F = M a = (M1 + M2) a
F = M2 g the net force accelerating the system
M2 g = (M1 + M2) a
a = M2 / (M1 + M2) g = 34 / (42) g = .81 g = 7.9 m/s^2