Question

Light travels at a speed of 2.0 × 10^8 m / s in a glass block. In the glass, the wavelength of the light is 4.0 × 10^-7 m. What is the frequency of the light? ​

Answer 1

Answer:

Frequency = 5*$10^{14}$ Hz

Given:

☞Speed of Light ( C ) = 2 * $10^8$ m/s

☞Wavelength of light ( $\lambda$ )= 4 * $10^{-7}$ m

Concept:

We know that,

Speed of Light in Vacuum = Frequency of light * Wavelength of light

C = f$\lambda$

Also,

1 seconds = 1 Hertz (Hz)

Explanation:

Applying the above concept and substituting the given values , we get:

2 * $10^8$ m/s = f * 4 * $10^{-7}$ m

f = $\dfrac{2 \times 10^8}{4 \times 10^{-7}}\:\:\dfrac{m/s}{m}$

f = $\dfrac{10\times10^14}{2}$ s

f = 5 * $10^14$ Hz

Therefore, the answer is 5 * $10^14$ Hz

Formulas for Mirror:

1) Mirror Equation

$\dfrac{1}{v}+\dfrac{1}{u}=\dfrac{1}{f}$

where,

• u = distance of object from the mirror
• v = distance of image from the mirror
• f($\dfrac{r}{2}$) = focal length of the mirror and r is the radius of curvature of the mirror

2) Magnification of Mirror

Magnification = $\dfrac{Height \: of \: image}{Height \: of \: object }$

Magnification = -$\dfrac{v}{u}$

Formulas for Lens:

1) Lens Formula

$\dfrac{1}{v}-\dfrac{1}{u}=\dfrac{1}{f}$

where,

• u = distance of object from the lens
• v = distance of image from the lens
• f($\dfrac{r}{2}$) = focal length of the lens and r is the radius of curvature of the lens

2) Magnification of Lens

Magnification = $\dfrac{Height \: of \: image}{Height \: of \: object }$

Magnification = $\dfrac{v}{u}$

3) Power of a Lens

Power = $\dfrac{1}{f}$

where,

• f = focal length of lens

Note : Focal length should be in metres or it should be converted in metres before substituting in Power of Lens formula