Concave Mirror Problem: Finding Image Distance, Height, and Magnification

[thatnewkid]

1. Homework Statement - A concave mirror with a focal length of 4.7cm has a 1.8cm object 9.4cm in front of it and i need to know the distance, height, and magnification of the image
also i need to figure out how to locate the image by drawing a ray diagram



2. Homework Equations - all i know of is 1/f=1/di+1/do and m=hi/ho=-di/do



3. The Attempt at a Solution - i can't figure any of this out at all, any assistance is greatly appreciated thanks!

 

[tiny-tim]

welcome to pf!

hi thatnewkid! welcome to pf!

2. Homework Equations - all i know of is 1/f=1/di+1/do and m=hi/ho=-di/do

ok, what do you think f di do m hi and ho stand for?

(and then fill in the numbers)

 

[thatnewkid]

hey thanks man
i know f stands for focal point
di for image distance
do for object distance
m for magnification
and i don't know about hi or ho

also i come up with unorthodox answers that make no sense so i think I'm doing something wrong :P

 

[tiny-tim]

hi ho thatnewkid!

hi stands for height of the image, and ho stands for height of the object

anyway, show us your full calculations, and then we'll see what went wrong, and we'll know how to help! ​

 

[thatnewkid]

1/f=1/di+1/do

1/4.7=1/di+1/9.4 so di equals .106383? for distance?

 

[Redbelly98]

1/f=1/di+1/do

1/4.7=1/di+1/9.4 so di equals .106383? for distance?

Almost, not quite. 1/di is equal to that number.

 

[thatnewkid]

2/1 then? I am sorry I am just so confused on this subject! :/

 

[rl.bhat]

2/1 then? I am sorry I am just so confused on this subject! :/

Take the reciprocal of .106383. That is the image distance.
In the textbook you will see a table showing the position of the object and the image with respect to the focal length. According to that when the object is at 2f, where should be the image?

 

[thatnewkid]

so that is 9.4
would it be right at 2f with the object?

 

[rl.bhat]

so that is 9.4
would it be right at 2f with the object?

Yes.

 

[thatnewkid]

wow ok thankyou haha
could you help me with the height and magnification?
hold on ill show you what i got so far...

 

[thatnewkid]

ok so m=hi/ho is equal to -9.4
now what?

 

[rl.bhat]

ok so m=hi/ho is equal to -9.4
now what?

m=hi/ho=-di/do