Answer:
The value is 

Step-by-step explanation:
From the question we are told that 
 The power rating of the bulb is 

 The frequency is 

 The percentage of the input power that is emitted as visible light is 

 
Generally the amount of power emitted as visible light is mathematically represented as 
 

=> 

=> 

Generally the amount of energy emitted as light is mathematically represented as 
 

Here n is the number of photon , h is the Planks constant with value 

Generally this power emitted as visible light is mathematically represented as 
 

=> 

=> 

=> 

=> 
