Why does LED2 light only half time compared to LED1?

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LED2 lights only half the time compared to LED1 due to the behavior of the transistor in the circuit. When the Base voltage is high, the transistor allows current to flow between the Emitter and Collector, effectively acting as a switch. This results in one LED receiving current while the other does not, depending on the Base voltage state. When the Base voltage is low, the circuit becomes open, stopping current flow and affecting the LEDs' operation. Understanding the transistor's function clarifies the differing light times of the two LEDs.
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Can anyone explain to me why LED2 light only half time compared to LED1? If Us=2sinωt volts
 

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Think about what the transistor does when Vs is "high".
 
it doesn't help me a lot...
 
That's okay, we'll review how the transistor functions in this circuit.

The transistor has 3 nodes:
The Base (left side of transistor)
The Emitter (lower-right of transistor)
The Collector (upper-right of transistor)

In this circuit, the transistor acts like a simple switch. When the Base voltage is high, you can treat it as a short between the Emitter and Collector. Which LED or LED's have any appreciable current going through them, if you short the Emitter to the Collector?

When the Base voltage is low or negative, you can treat the Emitter to Collector as an open circuit, with no appreciable current. If that's the case, which LED or LED's have an appreciable current going throw them?
 
I understand it now. Thx for the help!
 

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