Carbon-14 dating and Uranium Lead Dating

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EXPERIMENT – 10

AIM:

To determine the focal length of a convex lens using a vertical pin and a plane mirror by parallax removal method.

APPARATUS: 

Convex lens, plane mirror, vertical pin, stand for mounting and a scale.

THEORY:

If an object is kept at the focus of a convex lens, the light rays incident from the object on the lens become parallel to the principal axis after refraction. The refracted rays fall normally on the plane mirror and retrace their path to form an image on the object itself.
PROCEDURE:

1. Mount the pin, convex lens and the plane mirror on their respective stands as shown in the figure.

2. Adjust the height of the pin such that the tip of the pin and the optical centre of the lens are at the same horizontal level.

3. Adjust the position of the needle so that on looking through the lens at the image of the needle, there is no parallex between the object and the image.

4. Note the values of x₁ and x₂ from the scale.

5. Repeat the experiment for different positions of the convex lens.

PRECAUTIONS:

1.The tip of the pin and the optical centre of the lens should be at the same horizontal level.

2.The parallax should be properly removed.

RESULT:

The focal length of the lens is found to be --------

EXPERIMENT – 9

AIM:

To find the effort required to roll a roller up an inclined plane and to determine its MA and VR for different angles of inclination.

APPARATUS: 

An inclined plane, roller,weight box, pan, protractor and spring balance.

THEORY:

An inclined plane is a simple machine whose

 MA = Load/ Effort = L/E and 

VR= l/h where l= length of inclined plane and h= height of inclined plane.

PROCEDURE:

1. Fix the angle of inclination  of the inclined plane and note the values of l and h.

2. Note the weight of the roller with the help a spring balance and let it be L.

3. Tie the end of the string with the hook of the roller and pass it over the pulley. Tie the other end to the pan.

4. Note the weight of the empty pan. Let it be 'w'.

5. Add weights to the pan gradually till the roller just begins to slide. Let the total weights be  'W'. Hence the effort required is 'W+w'.

6. Repeat the experiment for different angles of inclination.

7. Calculate the MA and VR for each set.

PRECAUTIONS:

1. Clean and polish the surface of the inclined plane to minimise the friction.

2. Pulley should be oiled.

3. Pan should not touch the table or the inclined plane.

4. Increase the weight of the pan gradually.

5. The inclined plane should be knocked gently each time.

RESULT:

It is found that for each angle of inclination, MA < VR as the friction between the roller and the inclined plane increases the effort required.