Rafiq has heard that continued exposure to light for 10 days can change the colour of some blue dyes used to colour cotton clothing. He decides to test this. He takes a piece of clothing dyed with a blue dye which is suspected to lose colour on such exposure. He cuts the cloth into two pieces. Which experiment is likely to help him conclude if the dye indeed can change colour?
He should expose, for 10 days-

A. Both pieces under 2 identical lamps.
B. One piece under a lamp; keep the other in darkness.
C. One piece for 5 days and one for 10 days under identical lamps
D. One piece folded and one piece spread out under 2 identical lamps.

I think the answer is B

Ibelieve the correct answer would be c.

Answer: a charge of -1.0  × 10⁻⁴ c must be placed  at x = 26 m.the sign of the charge will be the same sign as the  -4.0  µc charge.======electricstatic force between two point charges  is given by    where k is coulomb's constant,  8.99×10⁹  n·m²/c², q₁ and q₂ are the point charges, and r is the distance between the two point charges.assign positive to q₁let q₁ =  6.0 µc, q₂ = -4.0  µc, q₀ represent the charge at the origin, and q₃ represent this new charge to place.the charge at the origin q₀ would experience the following force f₀₁ from q₁, with r = 6.0 m (note that 1  µc = 10⁻⁶ c)    the force from q₂    the force from q₃    the net force on the origin charge, q₀, has to be zero for no electrostatic forcehaving an equation where k and q₀ can be divided out of the equation will allow us to solve for q₃    isolating:     a charge of -1.0  × 10⁻⁴ c must be placed  at x = 26 m.the sign of the charge will be the same as the  -4.0  µc charge