Light, Microscopy, & Photography Notes

Light is a form of radiation that behaves as both a wave and individual particles called photons.
Electromagnetic radiation propagates at 90° angles between the electrical and magnetic components.
Radiation moves in all directions from the source.
The interaction of radiation with objects determines how we visually perceive the world.

Wavelength (λ): The distance between two peaks of a wave.
Amplitude: Height of a wave from its origin to its peak or trough.
Peak: Height of the wave from its origin.
Trough: Depth of the wave from its origin.
Frequency: The number of wavelengths per second.
Speed of Light (c): Wavelength x Frequency. $C = 299,792 \text{ km/s}$
The higher the frequency, the shorter the wavelength.
Wavelength is measured in nanometers (nm), where $1 \text{ nm} = 10^{-9} \text{ m}$ .
Unlimited variations of energy exist within waves due to the discrete nature of photons, leading to infinite wavelengths and frequencies.

Molecules are in constant motion based on their electric charge distribution, vibrating at their natural frequency.
Molecules absorb certain wavelengths and reflect others.
The reflected wavelengths are perceived as COLOR.
White light is a balanced combination of all frequencies in the visible spectrum.

Refraction occurs when light passes through an object, causing it to slow down.
- Shorter wavelengths are slowed but all pass equally at the same rate; the refractive index measures how much light is bent while passing through various materials. This bending of light results in phenomena such as the distortion of images or the formation of rainbows when light passes through water droplets.
The refractive index is the speed at which light travels through a material. This can be calculated to assist in evidence analysis.
The change in speed alters the wavelength, but the frequency remains constant.
Different refractive indices allow us to perceive objects.
- Same refractive index can cause items to appear unsee or gone due to the phenomenon known as optical invisibility, where light is bent around an object, making it undetectable to the human eye.
- While Diffrerent refractive index can cause the item to be enlarge, or bending
Dispersion: White light separates into its component frequencies when passing through an object like glass.

When light with multiple wavelengths passes through a lens, colors refract at slightly different angles (longitudinal refraction).
Shorter wavelengths refract more sharply than longer wavelengths.

Compound Microscope: Frame, Oculars, Course/Fine Adjustment Knob, Objectives, Stage
Stereo Microscope: Oculars, Objective, Adjustment Knobs, Stage

Compound Microscope: Retina, Ocular, Objective, Stage, Condenser, Illumination
- Hair: Used for studying hair structure and texture, as light can reveal pigmentation and morphology.
- Sperm: Ideal for examining motility and structure in biological studies.
  - things we can see through it
- Textile and bullets: Generally opaque materials where light cannot transmit effectively, limiting microscopic examination.
Light is crisscrossing in a microscope because multiple lenses bending (refracting) light paths to focus and magnify the image
- 📍 Lenses are curved → light bends at different angles.
  📍 High magnification → small changes in light angle = big visual changes.
  📍 Illumination techniques (like brightfield or phase contrast) can enhance this effect.
Stereo Microscope: Retina, Oculars, Prisms/Mirrors, Common Objective, Stage, Parallel Light
- incident light:the light that strikes the specimen before being magnified, which plays a crucial role in determining the clarity and detail of the observed image.
- Depth position:the location of the specimen within the focal plane, which can significantly influence the resultant image quality and depth of field in microscopy.
- Perfect for bullets, not blood samples

Total Magnification = Objective x Ocular
Greater magnification, shorter working distance
smaller magnification more working distance
Field of view= goes down as you increase mag and goes up when you decrease mag

Describes how long the shutter remains open.
- Very slow shutter speeds (5-10 seconds): low light, prolonged exposure.
- Slower shutter speeds (1/60): capture most images.
- Faster shutter speeds (1/250): bright days.
- Very fast shutter speeds (1/4000): "freeze time."

The f-stop is a ratio of the focal length to the diameter of the entrance pupil.
f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64

Paint with light is a photographic technique. An image is created by moving a light source or by moving the camera while using a long exposure time.