Optics

Electromagnetic Spectrum

• The Electromagnetic Spectrum is the range of all types of electromagnetic radiation, including visible light, radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays.

Definitions

• Reflection: The bouncing of light off a surface.

• Refraction: The bending of light as it passes from one medium to another.

• Angle of Incidence: The angle between the incident ray and the normal at the surface.

• Reflected Ray: The ray that bounces off the surface after reflection.

• Refracted Ray: The ray that bends after passing into a new medium.

• Angle of Reflection: The angle between the reflected ray and the normal.

Diagram for Reflection and Refraction

Properties of Images (SALT)

1. Plane Mirror:

   • Size: Same size as the object

   • Attitude: Upright

   • Location: Same distance behind the mirror as the object is in front of it

   • Type: Virtual

2. Concave Mirror:

   • Object at Different Locations:

     • Beyond C: Inverted, reduced, real, outside C

     • At C: Inverted, same size, real, at C

     • Between C and F: Inverted, enlarged, real, beyond C

     • At F: No image (parallel rays)

     • Between F and Mirror: Upright, enlarged, virtual.

3. Convex Mirror:

   • Size: Smaller than the object

   • Attitude: Upright

   • Location: Virtual, behind the mirror

   • Type: Virtual

4. Converging Lens:

   • Object at Different Locations:

     • Beyond 2F: Real, inverted, smaller

     • At 2F: Real, inverted, same size

     • Between 2F and F: Real, inverted, larger

     • At F: No image (parallel rays)

     • Between F and Lens: Virtual, upright, larger.

5. Diverging Lens:

   • SALT: Virtual, upright, smaller, located on the same side as the object.

Differences

• Concave Mirror: Curves inward, can produce real images depending on the object distance.

• Convex Mirror: Curves outward, always produces virtual images.

Converging vs. Diverging Lens

• Converging Lens: Thicker in the center, focuses light to a point; can produce real or virtual images.

• Diverging Lens: Thinner in the center, spreads light out; always produces virtual images.

Magnification Formulas

• Know how to use:

  • Magnification (M) = Image Height (hi) / Object Height (ho)

  • Thin Lens Formula: 1/f = 1/do + 1/di

Scale Diagrams

1. Converging Lens (f=45.0 mm, ho=12.5 mm, do=36.0 mm):

   • Calculate di and use SALT to describe the image.

2. Diverging Lens (f=10.0 mm, ho=12.0 mm, do=25.0 mm):

   • Similar calculation as above using SALT.

Index of Refraction

• Definition: A measure of how much a ray of light bends when entering a material.

• Formula: n = c / v (c = speed of light in vacuum, v = speed in medium).

• Relation to Density: The denser the medium, the higher the refractive index.

Speed of Light in Zircon

• Calculation: Speed = c / n; for n=1.92, speed of light = c / 1.92.

Index of Refraction Calculation

• Given Speed = 1.96 x 10^8 m/s, calculate using n = c / v with c = 3 x 10^8 m/s.

Total Internal Reflection

• Definition: The complete reflection of a light ray back into its original medium when it hits the boundary at an angle greater than the critical angle.

• Conditions: Light must travel from a denser to a less dense medium; angle of incidence must exceed the critical angle.

Parts of the Human Eye

• Cornea: Protects the eye and helps focus light.

• Lens: Focuses light onto the retina.

• Retina: Receives light and converts it to signals sent to the brain.

• Pupil: Regulates the amount of light entering the eye.

• Iris: Controls the size of the pupil.

Focusing Problems of the Eye

• Myopia (Nearsightedness): Light focuses in front of the retina; can be corrected with diverging lenses.

• Hyperopia (Farsightedness): Light focuses behind the retina; can be corrected with converging lenses.

• Astigmatism: Irregular lens curvature, causing distorted images; corrected with specially shaped lenses.