physics-class-12-unit-09-chapter-01-optics-general-introduction-l-1-9-xfgfj-vcuug

### <Success style="font-size:25px"> Optics General Introduction L-1 </Success>
### <primary style="font-size:24px"> Optics </primary>
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- 'Optics' deals with the Science and Technology which involve the propagation of light.

- The range of phenomena (or effects) and practical applications are very wide
- from most common application like spectacles for correction of vision, to modern high-spend optical fiber communication for transmission of multi -gigabits of information/data -

- Optics plays an important role!

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<footer style = "font-size: 18px"> $\rightarrow$ Optics General Introduction $\rightarrow$ <span style = "color:blue"> Optics </span> $\rightarrow$ Three Different Approaches $\rightarrow$ Ray Optics </footer>

### <Success style="font-size:25px"> Optics General Introduction L-1 </Success>
### <primary style="font-size:24px"> Ray Optics </primary>
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- **In Ray Optics**

- Propagation of Light is represented by "raye"
- A 'ray' is a. 'light path' along which the optical energy? flows; the direction of energy flow is indicated by the arrow sign.
- In a homogeneous medium,

- (i.e. a madium of uniform refractive index) Ray paths are straight lines.

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<footer style = "font-size: 18px">Optics $\rightarrow$ Three Different Approaches $\rightarrow$ <span style = "color:blue"> Ray Optics </span> $\rightarrow$ Ray Optics $\rightarrow$ Propagation of a Beam of Light </footer>

### <Success style="font-size:25px"> Optics General Introduction L-1 </Success>
### <primary style="font-size:24px"> Wave Optics </primary>
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- A beam of light comprises of large number of propagating waves - "a bunch of propagating waves"

- What type of waves?
- Electromagnetic Waves

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<footer style = "font-size: 18px">Bunch of Rays from Different Sources $\rightarrow$ Snell's Law $\rightarrow$ <span style = "color:blue"> Wave Optics </span> $\rightarrow$ Electromagnetic Waves $\rightarrow$ Light Waves Emanating from Different Sources </footer>

### <Success style="font-size:25px"> Optics General Introduction L-1 </Success>
### <primary style="font-size:24px"> Electromagnetic Waves </primary>
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- $\vec{E} =\hat{x} A \sin (\omega t-k z) $

- $ =\hat{x} A \sin \left(2 \pi f t-\frac{2 \pi}{2} z\right) $

- $ =\hat{x} A \sin k(v t-z)$

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<footer style = "font-size: 18px">Snell's Law $\rightarrow$ Wave Optics $\rightarrow$ <span style = "color:blue"> Electromagnetic Waves </span> $\rightarrow$ Light Waves Emanating from Different Sources $\rightarrow$ Quantum Optics </footer>

### <Success style="font-size:25px"> Optics General Introduction L-1 </Success>
### <primary style="font-size:24px"> Quantum Optics </primary>
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- Propagation of Light is described in terms of propagation of large number of tiny particle-like packets of optical energy called "Photons", which travel with the speed of light, $c$.

- The energy of a photon corresponding to light of a particular colour, with wavelength $\lambda$, is given by

- $E=h \frac{c}{\lambda}=h \nu$

- h - planck's constant (named after Max planck)

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<footer style = "font-size: 18px">Electromagnetic Waves $\rightarrow$ Light Waves Emanating from Different Sources $\rightarrow$ <span style = "color:blue"> Quantum Optics </span> $\rightarrow$ Bunch of Photons Emanating from Different Sources $\rightarrow$ Energy of a Photon </footer>

### <Success style="font-size:25px"> Optics General Introduction L-1 </Success>
### <primary style="font-size:24px"> Energy of a Photon </primary>
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- What is the energy of a photon corresponding to visible light?

- $ E=\frac{h c}{\lambda}$

- $h=6.6 \times 10^{-34} \{j} . \{s} $

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

- $ \lambda=600 \{nm}, \text { say for yellow light} $

- E=$\frac{6.6 \times 10^{-34} \times 3 \times 10^8}{600 \times 10^{-9}}$

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<footer style = "font-size: 18px">Quantum Optics $\rightarrow$ Bunch of Photons Emanating from Different Sources $\rightarrow$ <span style = "color:blue"> Energy of a Photon </span> $\rightarrow$ Energy of a Photon $\rightarrow$ At Extremely Low Powers </footer>

### <Success style="font-size:25px"> Optics General Introduction L-1 </Success>
### <primary style="font-size:24px"> Energy of a Photon </primary>
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- $ E=3.3 \times 10^{-19} \{J}$ (Extremely small!)

- What does this mean?

- If $10^{19}$ photons are incident on a screen or a photodetector, in $1 \{sec}$, it would correspond to a power of $3.3 \{W}$.

- $(E = 3.3 \times 10^{19} J) \times 10^{19} s^{-1}$

- = $3.3 Js^{-1}$
 
- Power  = 3.3 W

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<footer style = "font-size: 18px">Bunch of Photons Emanating from Different Sources $\rightarrow$ Energy of a Photon $\rightarrow$ <span style = "color:blue"> Energy of a Photon </span> $\rightarrow$ At Extremely Low Powers $\rightarrow$ E M Radiation </footer>

### <Success style="font-size:25px"> Optics General Introduction L-1 </Success>
### <primary style="font-size:24px"> At Extremely Low Powers </primary>
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- At extremely low powers, $\sim 10^{-15} \{W}$ or less, it is possible to count the no. of photons incident on a detector - "Photon counters"

- "Single photon sources"

- The output photons follow certain distributions and statistics with applications!

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<footer style = "font-size: 18px">Energy of a Photon $\rightarrow$ Energy of a Photon $\rightarrow$ <span style = "color:blue"> At Extremely Low Powers </span> $\rightarrow$ E M Radiation $\rightarrow$ Common Light Sources </footer>

### <Success style="font-size:25px"> Optics General Introduction L-1 </Success>
### <primary style="font-size:24px"> Speed of Light in Vacuum </primary>
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- $c_0 \simeq 3 \times 10^8 {m}/{s}(m.{s}^{-1})$

- (Precise value of $C_0=2.99792458 \times 10^8 m{s}^{-1}$ )

- In a material medium, light travels at a slower speed, given by

- $c= \frac{c_0}{n}$ (n - refractive index of the medium )

- $n = \frac{c_0}{c} >1$

- eg. glass $n \sim 1.5$, water $n=1.33$

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<footer style = "font-size: 18px">E M Radiation $\rightarrow$ Common Light Sources $\rightarrow$ <span style = "color:blue"> Speed of Light in Vacuum </span> $\rightarrow$ Course Module $\rightarrow$ Reference </footer>

### <Success style="font-size:25px"> Optics General Introduction L-1 </Success>
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- **(1) Ray Optics: 3 important phenomena**

- **1.** Reflection of light

- **2.** Refraction of light

- **3.** Dispersion of light

- **(2) Wave Optics: 3 important aspects**

- **1.** Interference of light

- **2.** Diffraction of light

- **3.** Polarization of light

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<footer style = "font-size: 18px">Common Light Sources $\rightarrow$ Speed of Light in Vacuum $\rightarrow$ <span style = "color:blue"> Course Module </span> $\rightarrow$ Reference $\rightarrow$ Some Reference Books </footer>