Certain x-rays have a frequency of 1.0×1019hz. calculate their wavelength in air.

For any electromagnetic wave, the relationship between frequency and wavelength is given by

where
is the wavelength
c is the speed of light (the speed of the electromagnetic wave)
f is the frequency

For the X-rays in our problem, the frequency is , while the speed of light is , so the wavelength of this radiation is

The answer is  a.first and third quarters 

Initial velocity,  u = 4.9 m/sfinal velocity = v m/sinitial height,  h₁ =  245 m    final height, h₂ = 0a = -9.8  m/s²time taken = t secondss = ut + 0.5at²⇒  (h₂-h₁) = ut + 0.5at²⇒  0-245 = 4.9t + 0.5×(-9.8)×t²⇒ -245 = 4.9t - 4.9t²⇒ 4.9t² -4.9t -245 =0solving it, we get   t = 7.59sv  = u +  at = 4.9 -9.8×7.59 = 4.9 - 74.38 = -69.48 m/svelocity is  69.48 m/s downward