Question

The time period of a light is 2.0 x10-s. The Wave length for this
wave is
​

Answer 1

Solution

Let f be the frequency of the photon and v be the wavelength of the photon

•From relation between frequency and time period:

f = 1/T..............[1]

•Also,

f = c/v...............[2]

•Equating equations [1] and [2],we get:

1/T = c/v

→v = T.c

We know that,

$\sf{c = 3 \times 10 {}^{8}ms {}^{ - 1} }$

Now,

$\sf{v = \frac{3 \times 10 {}^{8} }{2 \times 10} } \\ \\ \implies \: \boxed{ \sf{v = 1.5 \times 10 {}^{7} m}}$

Answer 2

Answer: λ = 0.06 m

Explanation:

Let the frequency of light be n and time period be T

Given,

T = 2 × 10¹⁰ second.

We know that there is a inverse relation between time period and frequency, i.e.

n = 1/T

n = 1/(2 × 10⁻¹⁰) Hz

n = 0.5 × 10¹⁰ Hz

n = 5 × 10⁹ Hz.

Now, let the wavelength of the light be λ.

Speed of light (c) = 3 × 10⁸ m/s

We know that,

c = nλ

3 × 10⁸ = 5 × 10⁹  × λ

3/5  × 10⁽⁸⁻⁹⁾ = λ

λ = 0.6 × 10⁻¹

λ = 6 × 10⁻² m

λ = 0.06 m