What is the wavelength of light is centimeters having a frequency of 1.5 Times 1

Question

What is the wavelength of light is centimeters having a frequency of 1.5 Times 10 s^-1? (The speed of light is 3.00 Times m/s.) 2.0 Times 10^-10 2.0 Times 10 5.0 Times 10^-9 5.0 Times 10^11 4.5 Times 10^28 Which of the following scientists first postulated that the sharp lines in the emission spectra of elements were caused by electrons going from high energy levels to low energy levels? Bohr Pauli de Broglie Hund Rutherford What is the wavelength of light emitted when the hydrogen atom undergoes a transition from n = 5 to n = 2? (R_H = 2.180 Times 10^-18 J) 663 nm 833 nm 546 nm 521 nm 434 nm

Explanation / Answer

12)

we know that

wavelength (lamda) = speed of light (c) / frequency (f)

so

using the given values

lamda = 3 x 10^8 / 1.5 x 10^18

lamda = 2 x 10-10 m

now

we know that

1 m = 100 cm

so

lamda = 2 x 10-10 x 100 cm

lamda = 2 x 10-8 cm

so

the answer is b) 2 x 10^-8

13) the answer is a) Bohr

14)

we know that

energy of light emitted is given by

E = Rh [ (1/n1)^2 - (1/n2)^2]

using given values

E = 2.18 x 10-18 [ ( 1/4) - (1/25)]

E = 4.578 x 10-19 J

now

we know that

E= h x c / lamda

here

h = plancks constant = 6.626 x 10-34

c = speed of light = 3 x 10^8

lamda = wavelength

so

4.578 x 10-19 = 6.626 x 10-34 x 3 x 10^8 / lamda

lamda = 4.342 x 10-7 m

lamda = 434.2 x 10-9 m

we know that

1 x 10-9 m = 1 nm

so

lamda = 434.2 nm

so

the answer is e) 434 nm

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