Question

Question C A spacecraft for extrasolar travel uses a sail to reflect light back toward the sun. At earth’s orbit the sunlight has an intensity of 1368 W/m2. The spacecraft has a mass of 2000 kg. a) [8] Determine the required sail to achieve an initial acceleration of the 9.8m/s2 b) [2] if it were black rather than reflective what would the initial acceleration be? Question D [8] Show that the units on the right side of eq 22-27 are those expected for c

how to do question D）

（Only help me to do question D）thanks）

Question A [4 x 4 marks] Early morning sunlight passes through polarizing sunglasses and hits a person’s eye lid (so they are not blinded by this light)

What orientation is the electric field at the persons eye?

The Poynting vector for this light is 650W/m2 West.

Find the electric field amplitude

Find the magnetic field amplitude.

Question B [ 4 x 4 marks] A photon with an energy of 10.2eV is absorbed by a hydrogen atom traveling in the opposite direction with a speed of 1000 m/s.

What is the energy in Joules of the photon?

What is the wavelength, frequency and speed of the photon

What is the momentum of the photon?

What is the speed of the atom after the photon is absorbed?

Answer 1

Okay, I see that you need help in Question (D) only.

(D)

c = 1 / sqrt ( u_oo)

where

u_o = 4 10^-7 N / A²

_o = 8.85 10^-12 F / m

notice that

1 N = Kg.m / s²

1 F = s⁴ A² / m ² kg

just use these units and values

let's not worry about values, let find the units

sqrt ( (Kg.m / s² . A² ) * ( s⁴ A² / m ³ kg))

cancel all the possible units, we are left with

sqrt ( s² / m² )

solving this square root, we can write

as

c = 1 / s/m

c = m/s

Therefore, we have proved that units of c , are m/s  

-------------------

c = 1 / sqrt ( 4 10^-7  Kg.m / s² . A² * 8.85 10^-12 s⁴ A² / m ³ kg)

c = 3e8 m/s