7 Light and Optics in Biology and Medicine Free Online FlashCards

What does a material’s refractive index describe?

The refractive index is defined by $n=c/v$, where $c$ is the speed of light in vacuum and $v$ is its speed in the material.

What happens to light’s frequency and wavelength at a material boundary?

Frequency stays constant across the boundary, while wavelength changes as light enters the new material.

What equation relates a thin lens’s focal length and object and image distances?

The thin-lens equation is $\frac{1}{f}=\frac{1}{d_o}+\frac{1}{d_i}$, where $f$ is focal length, $d_o$ is object distance, and $d_i$ is image distance.

Why doesn’t greater magnification always reveal more detail?

Magnification enlarges an image, but resolution determines whether nearby features appear distinct. Resolution depends on factors including wavelength and numerical aperture.

What is the main role of rods in vision?

Rods are highly sensitive to light and support vision in dim conditions.

What visual functions do cones support?

Cones provide color vision and fine detail, especially near the fovea.

What initiates phototransduction?

Light changes the shape of retinal in a visual pigment, initiating a biochemical cascade that changes photoreceptor signaling.

What does the Beer–Lambert relation connect?

The Beer–Lambert relation is $A=\varepsilon c\ell$: absorbance depends on molar absorptivity, concentration, and optical path length.

How does fluorescence change light energy and wavelength?

A fluorescent molecule absorbs higher-energy light and emits lower-energy light, typically at a longer wavelength.

What does Raman spectroscopy measure?

Raman spectroscopy measures small wavelength shifts in light scattered by molecules; the shifts provide information about molecular vibrations and chemical composition.

How can phase-contrast microscopy make transparent cells visible?

Phase-contrast microscopy converts differences in optical path through a sample into image contrast, revealing structures in transparent living cells without staining.

How does confocal microscopy improve contrast in thicker samples?

Confocal microscopy rejects much out-of-focus light, improving contrast in optical sections of thicker samples.