Red light on zinc ejects nothing. Orange, green, and blue eject nothing either. Even violet, the highest-frequency light your eye can see, ejects nothing. Just beyond the visible, in the ultraviolet, ejection begins.
You have met the minimum frequency twice: below it nothing, above it instant ejection. A quantity that important gets its own name. This lesson names it and shows where it sits for three real metals.
Light at or above the threshold frequency can eject electrons; light below it cannot.
Each metal has its own threshold frequency.
Zinc's threshold frequency lies in the ultraviolet, beyond visible light, so no visible light ejects electrons from zinc.
Sodium's threshold frequency lies inside the visible range, so violet light ejects electrons from sodium while red light does not.
Copper's threshold frequency lies even deeper in the ultraviolet than zinc's, so some ultraviolet lamps that eject electrons from zinc eject nothing from copper.
The threshold frequency is a fact about the metal, not about the lamp.
A lamp's frequency sits above sodium's threshold frequency but below zinc's. The lamp shines on a sodium plate and a zinc plate in turn. Which plate ejects electrons?
Light ejects electrons only from a metal whose threshold frequency is at or below the light's frequency.
For sodium, the lamp is above the threshold, so the sodium ejects electrons.
For zinc, the lamp is below the threshold, so the zinc ejects nothing.
Only the sodium plate ejects electrons.
Una finds that one green lamp ejects electrons from a first metal and not from a second metal. What does that tell her about the two metals' threshold frequencies?
Each metal has its own threshold frequency.
The first metal ejects, so its threshold frequency is at or below the green light's frequency.
The second metal does not eject, so its threshold frequency is above the green light's frequency.
The first metal's threshold frequency is lower than the second metal's.
Zinc's threshold frequency lies in the ultraviolet, beyond the visible range. Which light can eject electrons from zinc?
Xiomara says: 'Two different metals can have two different threshold frequencies.' Is Xiomara correct?
Sodium's threshold frequency lies inside the visible range. Zinc's lies in the ultraviolet. From which metal can visible light eject electrons?
A lamp ejects electrons from a potassium plate but not from an iron plate. Which statement about threshold frequencies is correct?
A theater floodlight can be set to any color of visible light, at any brightness. It points at a freshly cleaned zinc plate. Zinc's threshold frequency lies in the ultraviolet. How many electrons can the floodlight eject from the zinc?
For each metal, there is a minimum light frequency that can eject electrons from it. What is that minimum called?