Grade 10 SCIENCE | Quarter 2 Module 6 | Reflection in Mirrors • Ray Diagrams • Mirror Equation

Introduction

This tutorial will guide you through the concepts of reflection in mirrors, including the laws of reflection, characteristics of images, ray diagrams for curved mirrors, and the mirror equation. Understanding these concepts is crucial in Grade 10 Science, especially when dealing with optics and light behavior.

Step 1: Understand the Laws of Reflection

• The laws of reflection dictate how light behaves when it strikes a mirror.
• Key points to remember:
  • The angle of incidence is equal to the angle of reflection.
  • Both angles are measured from the normal (a line perpendicular to the mirror surface).

Practical Tip

• Use a protractor to measure angles accurately when conducting experiments.

Step 2: Explore Sample Problems for Laws of Reflection

• Practice problems help solidify your understanding of the laws.
• Example problem:
  • If a light ray strikes a mirror at a 30° angle to the normal, what is the angle of reflection?
  • Solution: The angle of reflection will also be 30°.

Common Pitfall

• Ensure you are measuring angles from the normal, not from the surface of the mirror.

Step 3: Characteristics of Images Formed in Plane Mirrors

• Images in plane mirrors have specific characteristics:
  • They are virtual (cannot be projected on a screen).
  • They are upright and the same size as the object.
  • The distance from the mirror to the image equals the distance from the object to the mirror.

Real-World Application

• This knowledge is useful in everyday situations, such as using bathroom mirrors or dressing mirrors.

Step 4: Study Curved Mirrors

• Curved mirrors can be concave or convex:
  • Concave Mirrors: Converge light rays and can produce real or virtual images.
  • Convex Mirrors: Diverge light rays and always produce virtual images that are smaller than the object.

Step 5: Create Ray Diagrams for Concave and Convex Mirrors

• Ray diagrams help visualize how light interacts with mirrors.

• For concave mirrors:

  1. Draw the principal axis.
  2. Mark the focal point (F) and center of curvature (C).
  3. Draw an object arrow perpendicular to the principal axis.
  4. Trace at least two rays to locate the image.

• For convex mirrors:

  1. Follow similar steps, noting that reflected rays appear to diverge from the focal point behind the mirror.

Practical Tip

• Use different colored pencils to differentiate between incident rays and reflected rays when drawing diagrams.

Step 6: Learn the Mirror Equation and Magnification Equation

• The mirror equation relates the object distance (d_o), the image distance (d_i), and the focal length (f):

  • ( \frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i} )

• The magnification (M) equation is used to find image size:

  • ( M = \frac{h_i}{h_o} = - \frac{d_i}{d_o} )
  • Where ( h_i ) is the height of the image and ( h_o ) is the height of the object.

Common Pitfall

• Pay attention to the signs in the equations, as they indicate whether the image is real or virtual.

Step 7: Solve Sample Problems for Mirror and Magnification Equations

• Practice with example problems to apply the equations effectively.
• Example problem:
  • If an object is placed 20 cm from a concave mirror with a focal length of 10 cm, find the image distance and magnification.
  • Solution: Use the mirror equation to find ( d_i ) and then apply the magnification equation.

Conclusion

In this tutorial, we covered the essential concepts of reflection in mirrors, including laws of reflection, image characteristics, ray diagrams, and the mirror equation. Mastering these topics will enhance your understanding of optics in physics. For further practice, consider solving more sample problems and drawing ray diagrams for various scenarios.