Lighting Calculation Help

[85mick85]

Looking some help with a question in an assignment I'm doing:

A workshop with 175 watt low pressure sodium vapour lamp at 3 meters above the floor.
The Sodium vapour lamp efficacy is 142.8 lumens per watt
Calculate illuminance and 4 m to side of lamp


Thanks in advance

 

[DavidSpark]

People will be far more likely to help if you show people you are will to learn and not just wanting the answer.

What are your thoughts on the question?

How do you think this would be answered?

 

[85mick85]

175-watt light

142.8 Lumens per watt

So

ΦV(lm) = P(W) × η(lm/W)

175 X 142.8 = 24990

24990 lumens for the light

I'm stuck with the rest of it hence why I'm asking for help.....

 

[85mick85]

Think iv got it,
175-watt light

142.8 Lumens per watt

So

ΦV(lm) = P(W) × η(lm/W)

175 X 142.8 = 24990

24990 lumens for the light

Lux at ground 3 meters below= 24990 /4π(3)²= 24876.9 lux


A²+B²=C²

3²+4²=C²

9+16=C²

9+16=25

√25= 5


Lux at 4 metes to the side of the light 24990 /4π(5)²= 79.5 lux


anyone know if it looks correct????

 

[samphier]

Was this correct. I have the same question on a piece of coursework.