Physics - Reflection, Refraction, Diffraction, Mirrors, Lenses

Reflection

The bouncing of a wave off a surface or boundary between two media.

Incident Ray

The light ray moving toward a boundary.

Reflected Ray

The light ray bouncing off a boundary.

Normal

An imaginary line perpendicular to the boundary at the point where the incident ray strikes.

Angle of Incidence (θᵢ)

Angle between the incident ray and the normal.

Angle of Reflection (θᵣ)

Angle between the reflected ray and the normal.

Law of Reflection

States that θᵢ = θᵣ (the angle of incidence equals the angle of reflection).

Specular Reflection

Occurs on a smooth surface where reflected light travels in the same direction.

Diffuse Reflection

Occurs on a rough surface where reflected light scatters in various directions.

Refraction

The bending of a wave as it passes through a surface or boundary between two media.

Angle of Refraction (θ₂)

Angle between the refracted ray and the normal in the new medium.

Index of Refraction (n)

Measure of the bending of a refracted ray; defined as the ratio of the speed of light in a vacuum to the speed in a medium.

Snell’s Law

n₁sin(θᵢ) = n₂sin(θ₂) (relationship between indices of refraction and respective angles).

Optical Density

How much light a material allows to pass through. Higher dense materials bend light more towards the normal.

Concave Lens (Diverging)

Thinnest at the middle, bends light rays away from the principal axis.

Convex Lens (Converging)

Thickest at the middle, bends light rays toward the principal axis.

Focal Point (F)

Point on the principal axis where refracted light converges or appears to diverge.

Focal Length (f)

Distance from the focal point to the lens center.

Lens Formula

1/f = 1/dₒ + 1/dᵢ (relationship between object distance, image distance, and focal length).

Magnification (M)

Ratio of image height to object height; M = hᵢ/hₒ = -dᵢ/dₒ.

Diffraction

Bending of waves as they encounter barriers or openings; waves spread out upon passing through small apertures.

Diffraction Grating

A surface with many parallel grooves used to bend light into different wavelengths.

Constructive Interference

Occurs when waves are in phase (path difference is an integer multiple of the wavelength).

Destructive Interference

Occurs when waves are out of phase (path difference is an odd multiple of half the wavelength).

Path Difference Formula

d sin(θ) = n λ (for constructive) and d sin(θ) = (n + ½) λ (for destructive).

Plane Mirror

A flat mirror that produces a virtual image that is the same size as the object and appears to be behind the mirror.

Concave Mirror

Curved inward, causing parallel rays of light to converge at a focal point. Can produce real or virtual images depending on the object's distance from the mirror.

Convex Mirror

Curved outward, causing parallel rays to diverge. Always produces virtual images that are smaller than the object, providing a wider field of view.

Concave Mirror - Image Location

When the object is beyond the focal point, the image appears real and inverted; when between the focal point and the mirror, the image is virtual, upright, and magnified.

Convex Mirror - Image Location

Always produces virtual images that are smaller than the object, appearing behind the mirror and providing a wider field of view.

Concave Lens (Diverging) - Image Location

Always produces virtual images that appear upright and smaller than the object, located on the same side as the object.

Convex Lens (Converging) - Image Location

When the object is placed beyond the focal point, the image appears real and inverted; when between the focal point and the lens, the image is virtual, upright, and magnified.