I think the answer is D, but I’m not at all sure :l
Answer:
f = 409 Hz
Explanation:
We have,
Length of the open organ pipe, l = 0.29 m
Frequency of vibration of second overtone, 
It is required to find the fundamental frequency of the pipe. For the open organ pipe, the frequency of second overtone is given by :

v is speed of sound
Let f is the fundamental frequency. It is given by :

The relation between f and f₂ can be written as :

So, the fundamental frequency of the pipe is 409 Hz.
Answer:
0.004 m
Explanation:
For light passing through a single slit, the position of the nth-minimum in the diffraction pattern is given by

where
is the wavelength
D is the distance of the screen from the slit
d is the width of the slit
Therefore, the width of the central maximum is equal to twice the value of y for n=1 (first minimum):

where we have
is the wavelength
D = 2.0 m is the distance of the screen
is the width of the slit
Substituting, we find

Answer
the medium does not change the speed of the on they should change.
Explanation:
The speed of the waves is constant for a given medium, depending on the physical properties of the medium,
When a wave is strapped on a wall of a medium it does not change the properties of the medium, the wave changes direction, but since the medium does not change the speed of the on they should change.