Q1: Science Long Test 2 Flashcards
Who was the first to make a theory on light?
Pythagoras and Plato (500-400 BC)
What was the theory?
Our eyes send probs to collect information and carry them back to us to see
What was Greek Philosopher Euclid’s theory on light?
Our eyes emit light rays
“optics”
What did Christian Huygen propose?
The first to propose the wave theory of light, light acts as a wave front.
What is the wave theory?
Light acts as a wave front. Light travels with the same speed as electromagnetic waves in a vacuum.
Who described light as a stream of particles and established the Corpuscular Theory of Light?
Sir Isaac Newton (1600-1700)
What is the Corpuscular Theory of Light?
It states that light travels in straight lines (“rays”) that can be reflected, refracted, and consists of 7 colors.
What did Heinrich Hertz discover in 1887?
The Photoelectric Effect, showing that light is capable of ejecting electrons from a metallic surface.
What type of light can cause the photoelectric effect according to Heinrich Hertz’s discovery?
Only high-frequency light
How did Heinrich Hertz’s discovery challenge existing theories?
It went against the wave theory of light.
What did Max Planck propose about electromagnetic radiation in 1900?
He proposed that EM radiation consists of discrete bundles of energy called “quanta” (singular: quantum) instead of continuous waves.
What concept did Albert Einstein apply from Max Planck’s theory in 1905?
Einstein used the quantum theory to explain the photoelectric effect, demonstrating that light quanta exist.
What are the particles of light named, and who named them?
The particles of light are named “photons,” a term coined by Gilbert N. Lewis in 1926.
What was the Ancient Greeks’ view of light according to Plato and Pythagoras?
They believed light originated in our eyes, and vision occurred when invisible probes were sent to gather information about far-away objects.
What did the Arab scientist Alhazen propose about light and vision?
He proposed that eyes collect light that falls on them, and that very few objects emit their own light.
What are the two sources of light according to ancient understanding?
Light-emitting objects (such as the Sun) and objects reflecting light.
How did Isaac Newton describe light?
Newton said light is made of tiny, atom-like particles called corpuscles.
What is refraction according to Isaac Newton?
Refraction is when a beam of light appears to bend as it passes through air into water.
What was discovered about light in the 19th century after Isaac Newton’s death?
Two beams of light that cross paths don’t interact with each other, and light creates interference patterns, which only waves can produce, not particles.
What happens when two wave patterns occupy the same space?
Light creates interference patterns, with complicated undulations due to the wave nature of light.
How did the understanding of light evolve in the 20th century?
Light was understood to transfer energy to atoms in metal in discrete packets (quanta).
How is light described in quantum mechanics?
Light sometimes behaves like a particle and sometimes like a wave.
What is the Incident Ray in the laws of reflection?
The ray that strikes the surface, pointing towards the surface.
What is the Reflected Ray in the laws of reflection?
The ray that rebounds from the surface, pointing away from the surface.
What is the Normal in the laws of reflection?
A line perpendicular to the surface at the point of incidence.
What is the angle of incidence
θi in reflection?
The angle between the incident ray and the normal.
What is the angle of reflection
θr in reflection?
The angle between the reflected ray and the normal.
What is the first law of reflection?
The angle of incidence is equal to the angle of reflection
What is the second law of reflection?
The incident ray, the normal, and the reflected ray all lie in one plane.
What happens when parallel rays strike a smooth, flat surface?
The reflected rays are parallel, and the reflection from the mirror is regular.
What happens when parallel rays strike a rough surface?
The reflected rays scatter in different directions because the normal at each point of incidence varies.
What is the definition of reflection?
he bouncing back of light into the same medium it has been traveling through after striking a surface.
What is Diffuse Reflection?
Reflection that occurs when light hits a rough surface and scatters in many directions. It is more common than regular reflection.
Can you give an example of Diffuse Reflection?
Walls, ceilings, and most objects with small imperfections on their surfaces exhibit diffuse reflection.
What is Specular (or Regular) Reflection?
Reflection from a smooth surface, where the reflected rays are parallel. It is important for devices like reflecting telescopes.
What is a mirror?
Any surface smooth enough to produce a regular reflection of light incident upon it.
What is a plane mirror?
Flat surface, mirrors at home
Spherical Mirror
flexing surface taken from the surface of a sphere
A concave mirror __ in the direction of the incident ray
curves inward
A convex mirror ___ to the incident ray
bulges outward
Describe a virtual image
It is behind a mirror, upright relative to the object, cannot be projected on a screen.
Describe a real image
In front of the mirror, can be upside down relative to the object/inverted
Plane mirrors are…
Virtual
Upright
Same size as the object
Convex mirrors are..
Virtual
Upright
Smaller than the object
Give the types of refraction & describe them
Dispersion - refraction of white light into separate colors (wavelengths)
Partial Refraction - usually comes together / some light may refract while others may reflect
Spherical lenses are..
a peace of glass / transparent material with one spherical surface.
Concave lenses are..
thicker at the edges than at the middle
This lense is thicker in the middle than at the edges, what is it?
Convex Lenses
