B, the surface of a flat table.
Answer:
The wavelength will be 4 cm, frequency will be 4.66 Hz and wave speed is 18.6 cm/sec
Explanation:
Given:
No. of crest = 13
No. of trough = 15
Time = 3 seconds
Hence, 1 crest or 1 trough = 
therefore,
13 C + 15 T = 
=
Time given 3 seconds
= 

2 cm distance is travelled is time period

Again wave will travel in 1 T = 4 cm
wave speed v =
= 
= 18.6 cm/s
In the single-slit experiment, the displacement of the minima of the diffraction pattern on the screen is given by

(1)
where
n is the order of the minimum
y is the displacement of the nth-minimum from the center of the diffraction pattern

is the light's wavelength
D is the distance of the screen from the slit
a is the width of the slit
In our problem,


while the distance between the first and the fifth minima is

(2)
If we use the formula to rewrite

, eq.(2) becomes

Which we can solve to find a, the width of the slit:
Answer:
For the first one, its B) cities B and C
I'm not so sure, but I hope this helps.
Answer:

Explanation:
Since
, we calculate the resistance rate by deriving this formula with respect to time:

Deriving what is left (remember that
):

So we have:

Which for our values is (the rate of <em>I(t)</em> is decreasing so we put a negative sign):
