Experiment 8 Measuring a human hair

Purpose:

the purpose of this experiment is to measuring a human hair with a laser. by this measurement, we can learn the concept of two-source interference of light, find the relationship among the wavelength, m, board distance. also anaylze the constructive interference, two slits, and destructive interference, two slits.

Equipment: one human hair(black hair), a paper punch card(for fix the hair). laser source, laser holder, hair holder, and a white board to obtain the light image.

Experiment and Data:

set up the equipment, make a clean hole in the card, and fix the hair in the middle of the hole, then use laser holder to fix laser source to make the laser directly go through the hole of the hair. then, use the white board in the other side of the hair to obain a laser two-slit interference image. final get the data of the distance of the white board from the hair, the wavelenght of laser, intergral number, and the distance of intergral number to calculate diameter of the hair.

in the experiment we get the data;

Ym = 3.7cm = 0.037+-0.0005m

wavelength = 670+-20nm

m = 5

r = 1.86 +-0.005m

from the equation Ym = (R*m*wavelength)/d, we can get d = (R*m*wavelength)/Ym = (1.86*5*670*10^-9)/0.037 = 1.68*10^-4m, we use microscope to measure the diameter of the hair is closed to 1.8*10^-4 m, our experiment value is very closed to the value we measure by the microscope, only have 6% error. so our experiment value make sense.

Conclusion:

from this experiment we get when two light source interference each other, just like the laser is divided by the hair into two light source. the two liht source interference each other, so it will create the constructive and desructive fringes in a distance of a board. we also find a relationship of Ym = (r*m*wavelength)/d is true, use this equation we can find the thickness of the hair.

Experiment 7 Lenses

Purpose：

the purpose of this lab is to measure the focus of the lens, find the relationship between object distance and image distance, and the relationship between object height and image height, also calculate M. then by view the direction of the image to determine the type of image.


Equation:

Obtics bench, Light, Object(must be a shape that is different on top and bottom), Object holder, Lens and lens holder, Viewing screen card, viewing screen holder.




Experiment and Data Collection:

before this experiment, we already know the focus point of the len we are used, then, set up the equipment, fix the len with a object holder in the middle, and on one side put the light source and object, on another side of the len put a white board to obtain the image. between the len and light source, the len and white board, we all put a meter to measure the distance. first of all we set up the object distance equal to 5 focus point, then, we move the white board on the other side of the len to fix it when we get a clear image. then we change to 4 focus point, and so on. we get the data below:

Object distance do /cm	Image distance di /cm	Object height ho /cm	Image height hi /cm	M	Type of image
5f = 70	22.5	3	1	-9/28	Inverted
4f =56	24.0	3	1.5	-12/23	Inverted
3f = 42	28	3	2.1	-2/3	Inverted
2f = 28	43	3	4.8	-43/28	Inverted
1.5f = 21	85	3	12.5	-85/21	Inverted

Change the object distance to 0.5 f. what happens to the image: we can not see the image for fact, we can see wirtual image, because the object distance is less than 0.5 f. take the card away and look throught the lens at the object to view the image. the images is upright.

Plot a graph of image distance, di vs object distance, do using centimeters, the shape of this graph should indicate an inverse relationship.



plot a graph of inverse image distance vs negative inverse object distance, the graph is below:

find the regression line or best-fit line for the data and record the slope and y-intercepts. we get from my graph, slope = 0.99 which is represent close to 1, and y-intercept represent the 1/f.

using the regression line from your graph and substituting in the axis values, write the equation that relats di and do.

we get equation: -1/do+1/di=1/f.

Conclustion: we get the conclustion from the experiment is, the image distance di is increase by the object distance do decrease. when the object distance is less than one focus point, the image height hi is increase by the objet distance do decrease. and for the object distance do is greater than the one focus point, all the image we get is real on the other side of the len, and all the real image are invert compare the real object. if the object distance do is less than the one focus point,
we will not get a real image in the other side of len, what we get is virual image, and the image is upright. by plot a graph of inverse image distance vs negative inverse object distance, we get a liear graph, then get get a relationship between object distance, image distance and focus : -1/do +1/di = 1/f.

Experiment 6 convex and concave

Purpose:

In this exploration we will explore the image formed by both a convex and concave mirror, and learn how to draw a graph to determine the image in the convex and concave mirror. and find the relationship between the object out of the mirror and the image inside the mirror. what is different between convex and concave mirror, and different phenomenon of concave and convex mirrors

Equipment:

convex mirror
concave mirror
object
ruler
worksheets adn the end of this exploration



Experiment:

Part A: Convex Mirror

1 Place an object in front of a convex mirror. Describe the image charachteristics as comopletely as you can
(a) the image appear smaller than the object
(b)the image upright is upright
(c)the image located relative to the position of the mirror and object closer to the mirror
(d) move the object closer to the mirror, the image get bigger when move close to mirror
(e)the image become smaller when move the object further from the mirror

then we draw the graph use three line as the picture below.



we get
h0 = 3.1+-0.05 cm
hi = 0.6+-0.05 cm
d = 6.1 +-0.05 cm
di = 1.9 +- 0.05 cm

m = (image height)/(object height) = (0.6 cm)/(3.1 cm) = 0.194 ± 0.0164 cm

after the first experiment, we get the experiment conclusion is same as our prophecy.

Part B:

place an object in front of a concave mirror.

(a) the image appear larger than the size as teh object
(b) the image is inverted.
(c) the image located relative to the same position of the mirror and object.
(d) move the object until is is close to the mirror. the image is get smaller than the image.
(e)move the object much further from the mirror than it was in step 1, perhaps as much as a meter away. when we move the object away from mirror, the image become smaller.

then we draw a graph of concave mirror with three line the graph show below:

h0 = 3.1 +- 0.05cm
hi = 1.7+-0.05cm
d0 = 10.4+-0.05cm
di = 2.4 +- 0.05cm

We have the magnification.
m = (image height)/(object height) = (1.75 cm)/(3.1 cm) = 0.565 ± 0.0185 cm


Conclusion:

we get from the experiment, for the convex mirror, the image appear smaller than the object before the mirror, and the image in the convex mirror is upright, and the image located relative to the position of the mirror is closer to the mirror.
for the concave mirror, the image appear larger than the object in the front of the mirror, and the image is inverted in the mirror, and the image located relative to the position of the mirror and object.