light and optics

What is light?

Light is a form of energy that travels in waves and can be detected by the human eye.

What speed does light travel at in a vacuum?

Approximately 300,000 kilometers per second (km/s).

What is the law of reflection?

The angle of incidence equals the angle of reflection.

What is the difference between specular and diffuse reflection?

Specular reflection is mirror-like and smooth; diffuse reflection scatters light in many directions.

What causes refraction?

Refraction occurs when light changes speed as it passes from one medium to another, bending its path.

What is the refractive index?

A measure of how much a material slows down light; higher refractive index means more bending.

What is total internal reflection?

When light hits a boundary at an angle greater than the critical angle and reflects completely inside the material.

What are concave and convex lenses?

Concave lenses are thinner in the middle and diverge light rays; convex lenses are thicker in the middle and converge light rays.

How does the human eye focus light?

The cornea and lens bend (refract) light to focus it on the retina.

What causes nearsightedness and how is it corrected?

Nearsightedness occurs when the eye focuses images in front of the retina; corrected with concave lenses.

What causes farsightedness and how is it corrected?

Farsightedness occurs when the eye focuses images behind the retina; corrected with convex lenses.

What is the electromagnetic spectrum?

The range of all types of electromagnetic radiation, including visible light.

What is dispersion of light?

The splitting of white light into its component colors, as seen in a rainbow or prism.

How do mirrors form images?

By reflecting light rays that appear to come from a virtual or real image location.

What is the difference between real and virtual images?

Real images can be projected on a screen and are inverted; virtual images cannot be projected and are upright.

What is the visible spectrum?

The portion of the electromagnetic spectrum that can be seen by the human eye.

What is a shadow?

A dark area where light is blocked by an opaque object.

What is a plane mirror?

A flat mirror that produces a virtual image the same size as the object.

What is the focal point of a lens or mirror?

The point where parallel rays of light converge or appear to diverge after passing through a lens or reflecting from a mirror.

What is a convex mirror?

A mirror that curves outward and produces a smaller, virtual, and upright image.

What is a concave mirror?

A mirror that curves inward and can produce real or virtual images depending on object distance.

What is magnification?

The ratio of the image size to the object size.

What is the critical angle?

The minimum angle of incidence at which total internal reflection occurs.

How do optical fibers use total internal reflection?

By trapping light inside the fiber, allowing it to travel long distances with little loss.

What is a prism used for in optics?

A transparent object that refracts light and separates it into its component colors.

What is the pupil in the human eye?

The opening that controls the amount of light entering the eye.

What is the retina?

The layer at the back of the eye that detects light and sends signals to the brain.

What role does the cornea play in vision?

It refracts light entering the eye to help focus images on the retina.

What is chromatic aberration?

A distortion in lenses caused by different colors of light bending by different amounts.

How does a camera lens work?

It focuses light to form a clear image on the camera sensor or film.

What is the difference between luminous and illuminated objects?

Luminous objects produce their own light; illuminated objects reflect light from other sources.

What is an opaque object?

An object that does not allow light to pass through.

What is a translucent object?

An object that allows some light to pass through but scatters it.

What is a transparent object?

An object that allows light to pass through clearly.

How does a lens form an image?

By bending (refracting) light rays to converge or diverge.

What is the difference between a convex and concave lens?

Convex lenses converge light rays; concave lenses diverge light rays.

What is an astigmatism?

A defect in the eye caused by an irregularly shaped cornea or lens that causes blurred vision.

What is a camera?

A device that uses lenses to focus light and capture images.

What is the function of the iris in the eye?

The colored part of the eye that controls the size of the pupil.

What is the near point of the eye?

The closest distance at which the eye can focus on an object clearly.

What is the far point of the eye?

The farthest distance at which the eye can see objects clearly.

What is a convex mirror commonly used for?

Vehicle side mirrors and security mirrors, because they provide a wider field of view.

What happens to light when it passes from air into water?

It slows down and bends toward the normal due to refraction. What is a real image?

What is the eyepiece (ocular lens)?

The lens you look through; usually magnifies 10×.

What is the body tube?

Connects the eyepiece to the objective lenses.

What is the revolving nosepiece?

Holds the objective lenses and rotates to change magnification.

What is the objective lens?

Lens closest to the specimen; comes in different magnifications (e.g., 4×, 10×, 40×).

What is the arm of a microscope?

The part you hold to carry the microscope; connects base and head.

What is the stage?

The flat platform where you place the slide.

What are stage clips?

Hold the microscope slide in place on the stage.

What is the diaphragm?

Controls the amount of light reaching the specimen.

What is the coarse adjustment knob?

Moves the stage up and down quickly for general focusing.

What is the fine adjustment knob?

Moves the stage slightly for sharp, detailed focusing.

What is the base of the microscope?

The bottom support of the microscope; used for stability.

What is the light source or mirror?

Provides light that passes through the specimen for viewing.

What is the condenser lens?

Focuses the light onto the specimen.

What is the mechanical stage?

A stage that can be moved precisely using knobs for better control.

Why should you start with the lowest objective lens?

It gives the widest field of view and makes it easier to locate the specimen.