A is the correct answer !!!
Answer:
Part a)

Part b)

Explanation:
Part a)
Level of sound = 75 dB
now we know that

here we know that

now we have


Part b)
Intensity of sound wave is given as

here we know that

so we have


now we know



now we have


Answer: 8400 J
Explanation:
The formula referenced in the question is:
Where:
is the thermal energy
is the mass of the water sample
is the specific heat capacity of water
is the variation in temperature
Solving:
This is the thermal energy released
Answer:
λ = 65.6 pm
Explanation:
Given that
λo = 65 pm
The initial energy of the electron

Now by putting the values




Eo=19.06 KeV
Given that kinetic energy KE= 0.84 KeV
Therefore the final energy
E= Eo - KE
E = 19.06 - 0.84 KeV
E= 18.22 KeV
The wavelength λ can be find as



λ = 6.56 x 10⁻¹¹ m
λ = 65.6 pm