Optics

• An EM wave arises from closely coupled oscillations of the electric field and the magnetic field.
• Photoreceptors are light-triggered biochemical changes of certain proteins in the retina, converting light into electrical impulses which travel along nerves into the brain.
• The optic nerve carries nerve signals to the brain.
• The pupil is an opening in the iris that determines how much light enters the eye.
• There are two types of photoreceptors: cones, which are sensitive to daylight and colour vision, and rods, which are sensitive to lower light intensities than cones.
• To focus on an object, eyes rotate so that an image forms on the fovea.
• The blind spot is where the optic nerve attaches to the retina.
• Negative q means a virtual image, which is one that can be seen but cannot be captured on a screen.
• Positive magnification means the same orientation as the object.
• Focal length is the length at which parallel rays from far away converge.
• Magnification value M is positive when image is rightside up, not inverted.
• Negative magnification means the image is inverted, relative to the object.
• Light is considered to behave both as a wave & a particle, a concept known as wave-particle duality.
• The particles of light are called photons, which often are referred to as "quanta of light", since they obey the laws of quantum mechanics.
• Photons are massless and travel in a vacuum at the speed of light, 𝑐.
• The rays are always perpendicular to the wave fronts, and in the direction of wave propagation.
• Chromatic aberration is caused by dispersion, where rays of different wavelengths are refracted at different angles.
• Spherical aberration occurs when rays of light passing through the outer parts of a lens are not focused at the same spot as rays passing through the centre.
• Astigmatism is a condition of non-uniform curvature of the cornea or lens surface.
• Most lenses in glasses are meniscus shaped, with negative power for near vision and positive power for distance vision.
• In a combination of lenses, the image from the first lens becomes the object for the second lens.
• The power of the corrective lens is determined by the distance between the far point and the eye.
• Optical defects of the eye can be corrected by using a lens system, such as glasses.
• Accommodation is the ability of the human eye to focus on both close objects and distant objects.