Soraya keeps a lab notebook with two columns, one for each model of light. Every experiment's result gets filed under the model that explains it. Some results fit only one column.
You have sorted the evidence and named the double behavior. This lesson makes the choice quick: given a situation, pick the model of light that is more useful for explaining it.
If the light is spreading, overlapping, reinforcing or canceling, pick the wave model. Stable bright-and-dark patterns and spreading after narrow gaps are wave work.
If the light is delivering energy in whole lumps, pick the photon model. Threshold frequencies, instant ejection, and counts of ejected electrons are photon work.
Here is one worked choice: dim ultraviolet light ejects electrons from zinc. Ejection runs one photon per electron, so the photon model is the more useful one there.
Useful does not mean true. Both models stay. The choice is about which picture explains the situation in front of you.
When a situation mixes both kinds of behavior, use each model for its own part. The same beam can spread at a slit and then eject an electron at a detector.
Dim ultraviolet light ejects electrons from a zinc plate. Which model of light is more useful for explaining this: the wave model or the photon model?
The result to explain is ejection: electrons leaving the metal under faint light.
Ejection runs on whole lumps: one photon, absorbed in one go, frees one electron.
A faint steady wave would need time to build up energy at an electron, and no delay is seen.
The photon model is the more useful model here.
At night, a distant streetlight seen through a fine mesh screen door spreads into a pattern of spots. Which model is more useful for explaining the pattern: the wave model or the photon model?
The result to explain is a stable pattern made by light spreading and overlapping after many fine gaps.
Spreading after narrow gaps is diffraction, and overlapping light reinforcing and canceling is interference.
Separate whole lumps do not cancel each other out, so the lump picture does not produce the pattern.
The wave model is the more useful model here.
Light from a blue laser passes through two narrow slits and makes a row of bright and dark bands on a screen. Which model of light is more useful for explaining the bands: the wave model or the photon model?
Laser light passing a thin human hair makes faint bright and dark bands beside the hair's shadow. Which model of light is more useful for explaining the bands: the wave model or the photon model?
A nickel plate under bright orange light ejects nothing, but the same plate under faint ultraviolet light ejects electrons. Which model of light is more useful for explaining this: the wave model or the photon model?
Doubling a lamp's brightness doubles how many electrons leave a potassium surface each second, while each electron's maximum energy stays unchanged. Which model of light is more useful for explaining this: the wave model or the photon model?
The fine-grooved side of a DVD spreads reflected light into rainbow bands. Which model of light is more useful for explaining the bands: the wave model or the photon model?
However bright a red floodlight is made, it ejects no electrons from a zinc plate. Which model of light is more useful for explaining this: the wave model or the photon model?
A cesium surface ejects electrons under faint blue light but none under bright red light. Which model of light is more useful for explaining this?
Moonlight seen through a thin woven curtain spreads into a cross-shaped pattern of spots around the bright Moon. Which model of light is more useful for explaining the pattern?
For explaining why a brighter lamp, above the threshold frequency, ejects more electrons each second from a sodium surface, the photon model is the more useful model. Which statement gives the reason?