' C ' is the only correct statement on the list. We don't know anything about diagram-x or diagram-y because we can't see them.
The refractive index of water is

. This means that the speed of the light in the water is:

The relationship between frequency f and wavelength

of a wave is given by:

where v is the speed of the wave in the medium. The frequency of the light does not change when it moves from one medium to the other one, so we can compute the ratio between the wavelength of the light in water

to that in air

as

where v is the speed of light in water and c is the speed of light in air. Re-arranging this formula and by using

, we find

which is the wavelength of light in water.
Answer:
a)1.37 s
b)∞ ( Infinite)
Explanation:
Given that
L= 47 cm ( 1 m =100 cm)
L= 0.47 m
a)
On the earth :
Acceleration due to gravity = g
We know that time period of the simple pendulum given as

Here

Now by putting the values

T=1.37 s
b)
Free falling elevator :
When elevator is falling freely then
( This is case of weightless motion)
Therefore

T=∞ (Infinite)
Please find attached photograph for your answer. Hope it helps. Please do comment
Answer:
B. 80 m/s²
Explanation:
F = ma
a = F/m = (40 N)/(0.5 kg) = 80 m/s²