Of the observations 1 to 8 listed, which four would be observed using only a triangular glass prism?

What a triangular glass prism can do

A triangular glass prism works by refraction. Because the refractive index depends on wavelength, it also causes dispersion, meaning different colours bend by different amounts.

Matching the prism to the listed observations

(1) Continuous spectrum with white light: Yes. White light contains many wavelengths, and a prism spreads them out into a continuous rainbow.

(4) Single bright line with monochromatic light: Yes. Monochromatic light has one wavelength, so there is no spreading into many colours. The prism just refracts it into one direction, giving a single line/spot.

(5) Red bends through a smaller angle than blue: Yes. In glass, shorter wavelengths (blue) typically have a larger refractive index than longer wavelengths (red), so blue is deviated more than red.

(7) Single spectrum when white light is incident perpendicular to the apparatus: Yes. A prism produces one dispersed spectrum (one continuous band). “Multiple spectra” is a diffraction grating effect, not a prism effect.

Why the other four are not prism-only observations

• (2) Bright-line spectrum with white light: bright lines come from emission sources (excited gases) or selective filtering, not a prism alone.
• (3) Interference pattern: needs two coherent paths, like double slits or thin films.
• (6) Red bends more than blue: opposite of normal dispersion in glass.
• (8) Multiple spectra at normal incidence: characteristic of a diffraction grating creating multiple orders, not a prism.

So the four observations for only a triangular glass prism are: 1, 4, 5, and 7.