2.2 How is Light Produced?

What are luminous objects?

• Objects that absorb all light.
• Luminous objects are objects that emit their own light.
• Objects that are only visible in darkness.
• Objects that reflect light from other sources.

How do we see non-luminous objects?

• We see non-luminous objects by their own emitted light.
• We see non-luminous objects by the light they reflect from luminous sources.
• We see non-luminous objects through thermal radiation.
• Non-luminous objects are visible only in complete darkness.

What is an incandescent light source?

• An incandescent light source is a light that produces illumination by heating a filament.
• A type of LED light that emits a blue hue.
• A light source that uses gas to produce illumination.
• A fluorescent light that relies on gas discharge for illumination.

What is a pro of incandescent light?

• High energy efficiency
• Cheap

• Long lifespan
• Instant brightness

What is a con of incandescent light?

• Much of the used energy produces heat instead of light.

• They are expensive.

• They break easily.

• Their light doesn't look good.

Which type of light uses electric discharge?

• Neon signs

• Fluorescent tubes
• LED lights
• Incandescent bulbs

What is phosphorescence?

• Phosphorescence is a chemical reaction that produces heat.
• Phosphorescence is the emission of light in gases.

• Phosphorescence is the process by which a substance absorbs light and re-emits it over an extended period.
• Phosphorescence is emission of light using batteries.

What is fluorescence?

• Fluorescence is the reflection of light from a surface.
• Fluorescence is the immediate emission of light by a substance that has absorbed UV light.

• Fluorescence is the emission of light from a flower.

• Fluorescence is the absorption of sound waves by a material.

What is a pro of fluorescent light?

• Higher light output

• Energy efficiency
• Cheap

• High heat output

What is a con of fluorescent light?

• Breaks easily.

• Produces UV radiation.

• Only available in some colors.

• Contains hazardous materials like mercury.