Answer:
the wavelength λ of the light when it is traveling in air = 560 nm
the smallest thickness t of the air film = 140 nm
Explanation:
From the question; the path difference is Δx = 2t (since the condition of the phase difference in the maxima and minima gets interchanged)
Now for constructive interference;
Δx= 
replacing ;
Δx = 2t ; we have:
2t =
Given that thickness t = 700 nm
Then
2× 700 = --- equation (1)
For thickness t = 980 nm that is next to constructive interference
2× 980 = ----- equation (2)
Equating the difference of equation (2) and equation (1); we have:'
λ = (2 × 980) - ( 2× 700 )
λ = 1960 - 1400
λ = 560 nm
Thus; the wavelength λ of the light when it is traveling in air = 560 nm
b)
For the smallest thickness 
∴ 
Thus, the smallest thickness t of the air film = 140 nm
Answer:
The linear velocity of the racquet at the point of contact with the ball is 6 m/s.
Explanation:
Given;
angular velocity of the racquet, ω = 12 rad/s
distance of strike, r = 0.5 m
The linear velocity of the racquet at the point of contact is given by;
V = ωr
V = (12)(0.5)
V = 6 m/s
Therefore, linear velocity of the racquet at the point of contact with the ball is 6 m/s.
The results may differ due to resistive forces that may be affecting the system by decelerating it or any other external forces that might accelerate it a bit.Or the timing could be a little inaccurate.
First we have to convert:
75 km / h ( * 3.6 ) = 270 m/s
18 m/s = 64.8 m/s
d = v i · t + 1/2 a · t²
v = v i + a t
-----------------------------------
4000 = 64.8 · t + 1/2 a · t²
270 = 64.8 + a t
a = ( 270 - 64.8 ) / t
a = 205.2 / t
4000 = 64.8 t + 1/2 · ( 205.2 / t ) · t²
4000 = 64.8 t + 102.6 t
4000 = 167.4 t
t = 4000 : 167.4 = 23.89 s
a = 205.2 : 23.89 = 8.58 m/s²
Answer: His average acceleration was 8.58 m/s²
