Question

ANSWER ONLY IF YOU'RE SURE



The illumination from a source of light varies inversely as the square of
the distance from the source of light. When the distance from a source
of light is tripled, how does the illumination change?

Answer 1

Answer:

Light intensity at 2 feet is 8 lumens

Explanation:

Let intensity be  

i

Let the distance from light source be  

d

Let the constant of association be  

k

Then:  

i

=

k

d

2

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Given condition

→

i

=

8

at  

d

=

3

⇒

8

=

k

3

2

Multiply both sides by  

3

2

⇒

8

×

3

2

=

k

3

2

×

3

2

=

72

Then:  

i

=

72

d

2

'~~~~~~~~~~~~~~~~~~~~~~~~~

So at 2 feet we have:  

i

=

72

2

2

=

18

Light intensity at 2 feet is 8 lumens

Explanation:

Let intensity be  

i

Let the distance from light source be  

d

Let the constant of association be  

k

Then:  

i

=

k

d

2

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Given condition

→

i

=

8

at  

d

=

3

⇒

8

=

k

3

2

Multiply both sides by  

3

2

⇒

8

×

3

2

=

k

3

2

×

3

2

=

72

Then:  

i

=

72

d

2

'~~~~~~~~~~~~~~~~~~~~~~~~~

So at 2 feet we have:  

i

=

72

2

2

=

18

Step-by-step explanation: