Physics - What is light? Refraction, reflection and absorption of light.

Summary

This video explores the fascinating journey of light and its interaction with objects to create color and vision. It delves into how the protein rhodopsin in our eyes processes light, the principles of reflection and refraction, and the optical phenomena that shape our perception. From how different wavelengths produce color to how light behaves when passing through various mediums, the video explains concepts like total internal reflection, rainbows, and even optical illusions like mirages. The script provides an insightful understanding of the science behind vision and light's role in how we perceive the world.

Takeaways

• 😀 Rhodopsin is a protein in the retina that responds to visible light by generating an electro-chemical signal, creating a visual representation of the world in the brain.
• 🌈 Visible light has wavelengths between 380 nm and 750 nm, and each wavelength corresponds to a different color perception.
• 🔍 Color is a result of the light an object reflects, not a property of the object itself.
• 💡 Objects appear different colors depending on how they absorb or reflect various wavelengths of light.
• 🖤 Black is the absence of light, while white is the reflection of all visible wavelengths equally.
• 🟥 An object appears red when it reflects the longest wavelengths and absorbs others, while a green object will appear black under red light due to no reflected green wavelengths.
• 🔄 Reflection follows the rule that the angle of incidence is equal to the angle of reflection, with the angle measured relative to the normal of the surface.
• ❄️ A polished surface reflects parallel rays in the same direction, while rough surfaces cause diffuse reflection, spreading light in all directions.
• 🔮 To see your reflection in a mirror, light must diffuse off you, reflect off the mirror, and return to your eyes as parallel rays.
• 🌊 Light bends when passing from one medium to another. It slows down in denser media, causing refraction towards the normal, and bends away when moving from denser to less dense media.
• 🌈 Rainbows are created by the refraction and total internal reflection of sunlight in water droplets, breaking white light into the full spectrum of colors.
• 🌡️ A mirage occurs due to the refraction of light in hot air layers above asphalt, creating an optical illusion of water on the road.

Q & A

What is rhodopsin, and where is it found?

Rhodopsin is a protein found in the retina of the eye. It plays a key role in visual perception by reacting to light and creating an electro-chemical stimulus.

What is the range of wavelengths that can affect rhodopsin?

The wavelengths that affect rhodopsin range from 380 to 750 nm, which corresponds to the visible light spectrum.

How does visible light create a visual representation in our brain?

When light falls on rhodopsin in the retina, it breaks down, triggering an electro-chemical stimulus that the brain interprets as a visual representation of the world.

Why do objects appear different colors under different light sources?

An object's color depends on the wavelengths of light it reflects. If it absorbs certain wavelengths and reflects others, we perceive the reflected wavelengths as the color of the object.

What happens to an object when it is exposed to red light but was green previously?

If the object was green and is exposed to red light, it will appear black because the object absorbs all wavelengths except green, which isn't present in red light.

What is the difference between reflection from a polished surface and a rough surface?

A polished surface reflects light in parallel rays, while a rough surface causes diffuse reflection, scattering light in all directions.

How does total internal reflection occur?

Total internal reflection happens when light passes from a denser to a less dense medium at a high enough angle, causing the light to bounce back into the denser medium instead of refracting.

Why do we see a rainbow after light passes through a water droplet?

A rainbow forms when white light enters a water droplet and refracts, breaking up into its constituent colors. The light then reflects inside the droplet before exiting, refracting again to form the rainbow.

What causes the optical illusion of a mirage on a hot day?

A mirage occurs when light travels through hot air near the ground, which is less dense than cooler air above. This causes total internal reflection, making it appear as if there is water on the road.

What is the critical angle of total reflection?

The critical angle is the specific angle of incidence beyond which total internal reflection occurs, and light is completely reflected within the denser medium.