7 Geometric Optics Free Online FlashCards

When is the ray model of geometric optics useful?

Geometric optics models light as straight-line rays and works well when light interacts with objects much larger than its wavelength.

How do specular and diffuse reflection differ?

Specular reflection is orderly reflection from a smooth surface; diffuse reflection sends light in many directions from a rough surface.

How is a material’s refractive index defined?

The refractive index is the speed of light in vacuum divided by its speed in the material: $n=\frac{c}{v}$.

How does a ray bend when it enters a higher-index material?

On entering a higher-index material, a ray bends toward the normal; on entering a lower-index material, it bends away from the normal.

What equation describes refraction at a boundary?

Snell’s law relates the indices and ray angles at a boundary: $n_1\sin\theta_1=n_2\sin\theta_2$. The angles are measured from the normal.

What distinguishes a real image from a virtual image?

A real image forms where rays actually converge and can be projected onto a screen. A virtual image forms where rays only appear to originate and cannot be projected onto a screen.

How does a ray diagram locate an image?

Trace at least two predictable rays from the object’s top. The image tip lies where the rays intersect, or where their backward extensions intersect for a virtual image.

What equation relates object distance, image distance, and focal length?

For spherical mirrors and thin lenses, the object and image distances satisfy $\frac{1}{d_o}+\frac{1}{d_i}=\frac{1}{f}$.

What do the sign and value of linear magnification indicate?

Magnification is $m=\frac{h_i}{h_o}=-\frac{d_i}{d_o}$. Positive $m$ means upright; negative $m$ means inverted.

What image does a plane mirror form?

A plane mirror forms an upright, virtual image the same size as the object, the same distance behind the mirror as the object is in front.

How are a spherical mirror’s focal length and curvature radius related?

In the paraxial approximation, a spherical mirror’s focal length is half its radius of curvature: $f=\frac{R}{2}$.

What image does a convex mirror form, and what is one use?

A convex mirror forms a virtual, upright, reduced image. Its wide field of view makes it useful in security and vehicle mirrors.