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State the laws of reflection of light - Leaving Cert Physics - Question b - 2012
Question b
State the laws of reflection of light. How would you estimate the focal length of a concave mirror? The diagram shows an object O in front of a concave mirror, who... show full transcript
Worked Solution & Example Answer:State the laws of reflection of light - Leaving Cert Physics - Question b - 2012
Step 1
State the laws of reflection of light.
Answer
- The incident ray, the reflected ray, and the normal at the point of incidence all lie in the same plane.
- The angle of incidence is equal to the angle of reflection (i = r).
- The angle of incidence (i) is measured between the incident ray and the normal line, while the angle of reflection (r) is measured between the reflected ray and the normal line.
Step 2
How would you estimate the focal length of a concave mirror?
Answer
- Place a distant object (such as a tree) in front of the concave mirror.
- Adjust a screen until the image of the object is as sharp as possible.
- Measure the distance from the mirror's surface to the screen, which gives the approximate focal length.
- The focal length (f) can also be calculated using the formula: where r is the radius of curvature, measured from the center of curvature to the mirror's center.
Step 3
Copy and complete the diagram to show the formation of the image of the object O.
Answer
- Draw two rays from the object O:
- The first ray travels parallel to the principal axis and then reflects through the focus F.
- The second ray travels through the focus F and reflects parallel to the principal axis.
- Mark the point where the two reflected rays intersect to indicate the formation of the image.
- Label the image as 'Image' on the diagram.
Step 4