All black surfaces is the correct answer
You look up the element in the periodic table. Subtract the atomic number (small number) from the mass number (big number). The answer is the number of neutrons.
Answer:
1)every planet move in elliptical path.
-- Charges with the same sign repel each other.
-- Charges with different signs attract each other.
-- This is called the "electrostatic force".
-- There's another set of forces called "magnetic forces", but
-- there's no such thing as "electromagnetic force".
Answer:
C). Refraction
Explanation:
When light enters from one medium to another medium then it changes it's direction from its initial direction
the phenomenon of changing the direction due to change in the medium is known as Refraction of light
So here we know that when light strikes an interface which separates two medium then due to change in the medium we will have

so here we have
= two angles of the light in two mediums
= two refractive index of the two mediums
So correct answer will be
C). Refraction