The colour we see is a measure of the wavelengths of light nor absorbed by the cloth. We would call the colour of the cloth blue if it absorbed longer wavelengths of yellow/orange/red. Sunlight contains all the visible wavelengths. Whatever is not absorbed is reflected.
Complete question:
Two 10-cm-diameter charged rings face each other, 21.0 cm apart. Both rings are charged to +40.0 nC. What is the electric field strength at the midpoint between the two rings ?
Answer:
The electric field strength at the mid-point between the two rings is zero.
Explanation:
Given;
diameter of each ring, d = 10 cm = 0.1 m
distance between the rings, r = 21.0 cm = 0.21 m
charge of each ring, q = 40 nC = 40 x 10⁻⁹ C
let the midpoint between the two rings = x
The electric field strength at the midpoint between the two rings is given as;

Therefore, the electric field strength at the mid-point between the two rings is zero.
First question: 800J
Second question: 20.4m
Direction!
Velocity is a vector quantity and speed is a scalar quantity. Vector quantities includes both magnitude and direction, while scalar quantities only have magnitude. :)
Answer:
The initial energy level = 6
Explanation:
Photon wavelength is proportional to energy. The wavelength of emitted photons is related to the energy levels of the atom as given by the Rydberg formula:
ₕ₁₂
(1/λ) = Rₕ [(1/n₂²) − (1/n₁²)]
where n₂ = final energy level = 2
n₁ = initial energy level = ?
Rₕ = Rydberg's constant = 1.097 × 10⁷ m⁻¹
λ = wavelength = 410 nm = 410 × 10⁻⁹ m
1/(410 × 10⁻⁹) = (1.097 × 10⁷) [(1/2²) − (1/n₁²)]
0.223 = [(1/4) − (1/n₁²)]
(1/n₁²) = 0.02778
n₁² = 1/0.02778 = 36
n₁ = 6.