Plese i am new
on the basis of bohr's model, the radius of the 3rd orbit
is -
(a) equal to the radius of first orbit
(b) three times the radius of first orbit
(c) five times the radius of first orbit
(d) nine time the radius of first orbit

Explanation:

On the basis of Bohr's model, the radius of the nth orbit is  

r = a₀n²  

where a₀ is a constant called the Bohr radius.  

r₃\r₁ = (a₀ × 3)²/(a₀ × 1)² = 9/1 = 9

The radius of the third Bohr orbit is nine times the radius of the first orbit.

i believe the answer is true.