I think it because of UV rays ultra violet ray which can make their colors different
Answer:
Magnitude of the magnetic field inside the solenoid near its centre is 1.293 x 10⁻³ T
Explanation:
Given;
number of turns of solenoid, N = 269 turn
length of the solenoid, L = 102 cm = 1.02 m
radius of the solenoid, r = 2.3 cm = 0.023 m
current in the solenoid, I = 3.9 A
Magnitude of the magnetic field inside the solenoid near its centre is calculated as;

Where;
μ₀ is permeability of free space = 4π x 10⁻⁷ m/A

Therefore, magnitude of the magnetic field inside the solenoid near its centre is 1.293 x 10⁻³ T
This is a non testable question because it cannot be answered by doing an experiment. But it could be modified for example Dogs are more obedient then cats.
I think it is c density and temperature
Because although they cannot see it, they can see it's influence on objects that can be seen, and it's effects.