optics entire review

properties of light

1. light energy travels very fast (c = 3.0 × 10^8 m/s)

2. light travels in a straight line but also as waves (electromagnetic waves)

3. radiates ( no medium needed)

electromagnetic spectrum

red has long waves but low energy

violet has high waves and high energy

radiation

form of electromagnetic energy ex. sunshine, x rays, radiant heating systems

light energy

form of electromagnetic radiation of a wavelength

photons - tiny packets of energy produced from the movement of atoms

incandescence

production of light as a result of high temp.

• incandescnes light bulbs

electric discharge

process of producing light by passing an electric current through a gas

• neon signs

• lightening

fluorescence

(phosphors — hg → UV → phosphors) immediate

immediate emission of visible light, a result of the absorption of UV light

• glow in the dark stickers

• fluorscence lights

phosphorescence

producing light by absorption of UV light, resulting in the emission of visible light over an extended period of time

glow in the dark stickers

chemi and bioluminscence (chemical reaction)

direct production of light as the result of a chemical reaction w little or no heat produced

chemi - glow sticks

bio - fireflies

triboluminscennce

production of light from friction, result of scratching crushing or rubbing certain crystals

leds

light produced as a result of an electric current flowing in semiconductors

laser

has one continuous straight line, same wavelength so same colour

laws of reflection

angle of incidence = angle of reflection

Oi and Or and normal lies in the same place

SALT

size - large small same

attitude - upright or inverted

location - object / image

type - virtual or real

virtual - light doesn’t meet and doesn’t interept usually the same orientation as an object can’t be projected, divergent

real - light converges and meets at a point

electromagnetic spectrum from highest to lowest

Gamma Rays

• • Used in cancer treatment (radiotherapy).

  • Emitted by radioactive substances and nuclear reactions.

  • Gamma-ray bursts in space.

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2. X-Rays

• • Medical imaging (e.g., X-rays of bones).

  • Airport security scanners.

  • Used in astronomy to observe stars and black holes.

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3. Ultraviolet (UV) Light

• • Causes sunburn (UV radiation from the Sun).

  • Sterilization of medical equipment.

  • Black lights and some insect traps.

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4. Visible Light

• • Rainbow colors (ROYGBIV: red, orange, yellow, green, blue, indigo, violet).

  • Sunlight, light bulbs, and lasers.

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5. Infrared (IR) Radiation

• • Heat emitted by objects (e.g., humans, stoves).

  • Used in remote controls and thermal imaging cameras.

  • Infrared astronomy to detect heat from celestial objects.

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6. Microwaves

• • Microwave ovens.

  • Satellite communications (e.g., GPS, weather forecasting).

  • Radar systems.

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7. Radio Waves

• • AM/FM radio broadcasting.

  • Television signals.

  • Cell phone and Wi-Fi communication.

convex lenses

converge

f’ (secondary focus) is on the left side, principal f is on the right side

IN: parallel to pa OUT: through princiapl f

IN: through secondary f OUT: parallel to pa

IN and OUT through optical centre

concave lenses

diverge

principal f is on the left side, secondary is on right (where light seems to not focus)

IN: parallel to Pa, OUT: as if it had come through princiap f

IN: appears to pass through F’, OUT: parallel to PA

IN and OUT through optical centre.

index of refraction

ratio of speed of light in a vacuum to speed of light to a medium

why doesn’t n go below 1?

bc it would imply that the speed of light is going faster than it is in a vacuum which is not possible due to enstian’s theory

c -

fastest light in a vacuum (light can travel)

v -

v and n

speed in a specific medium

v and n are proportional, if n increases, v descreased

apparent depth

Apparent depth refers to the depth at which an object appears to be when viewed from above the surface of a transparent medium (like water or glass).

This is due to the refraction of light as it passes from the water (or another medium) into the air, making the object appear closer to the surface than it actually is.

Explain why the index of refraction of a vacuum is n=1. Use the word “atoms”

and “Snell’s Law

In a vacuum, since n=1n=1, Snell’s Law implies that there is no refraction (or bending) of light as it enters or exits the vacuum from another medium.

This is because there are no atoms in a vacuum to alter the speed or direction of light.

why does n have no units

Because c and v are both speeds and can be expressed in the same units of m/s, the units in the equation divide out, so n has no units.

why does tir have light bending away from the normal

light needs to bend away from the normal in order for light to reflect back on itself,

because at higher angles of incidence, the light can no longer refract into the less dense medium. Instead, it reflects back into the denser medium, where the angle of incidence and reflection are the same.

fibre optics are used for

Fibre optics uses light to send information through a glass cable.

To keep the light from escaping, the cable needs a small critical angle.

This ensures that the light stays inside the cable by reflecting off the walls.

Materials like high-purity glass and certain plastics, like Lucite, have a small critical angle and are used for this purpose.

electromagnetic wave spectrum order highest to lowest

increase in photon energy, decrease in wavelengths

gamma → x rays → ultraviolet → visible light → infrared radiation → microwaves → radio waves

applications for electromagnetic types of light

gamma - used in cancer radiation treatment

x rays - used to see through the body

ultraviolet - gel manicures

visible light - sunlight, any light we can see

infrared radiation - remote controls, fibre optic cables

microwaves - microwaves, wi-fi routers, bluetooth

radio waves - am and fm radio broadcasting, tv broadcasting, gps

why is Rudolph’s nose red n not blue?

• Red light scatters less in fog and snow compared to blue light, which is why red is used for stop signs and tail lights.

• meaning a blue glow would be harder to see in fog or snowy conditions.

what is ‘scattering’

• light waves interact with small particles; causing the light to spread out in different directions.

  The # of scattering depends on the wavelength of the light.

• Shorter wavelengths (like blue or violet light) scatter more because they are closer in size to the particles causing the scattering.

• • Longer wavelengths (like red light) scatter less because they are much larger than the particles and pass through more directly.

y is the sky blue.. why r sunsets red

• sunlight passes through the atmosphere. The blue wavelengths of sunlight scatter in all directions, making the sky appear blue.

• At sunrise or sunset, the sun is lower in the sky, so light travels through more atmosphere. The blue light scatters out, leaving the longer red and orange wavelengths, which is why sunsets are red.

he sky doesn't appear violet because:

• The sun emits less violet light compared to blue.

• Our eyes are more sensitive to blue light than violet light.