g If we decreased the wavelength by a factor of 2 and also increased the distance D by a factor of 2, the fringes on the screen would be...

y = y₀ / 4

Explanation:

In a double slit experiment the constructive interference lines are given by

          d sin θ = m λ

if we use trigonometry

          tan θ = y / L

as in these experiments the angles are very small

          tan θ = sin θ /cos θ = sin θ

we substitute

         sin θ = y / L

          d y / L = m λ

let's use a subscript "o" for the initial values  

          I = m λ₀ L /d₀

They ask us to decrease the wavelength by 2

           λ =  λ₀ / 2

the distance in the slit is increased by a factor of two

         d = 2 d₀

we substitute

          2d₀  y/L = m  λ₀/2

          y = m  λ₀ L/d₀    ¼

          y = y₀ / 4

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.