class 10 physics notes

 Real Image vs Virtual Image                                                                                                                                                                 1️⃣Real Image                                                                                                                                                                                                        • Formation: Light rays actually meet (converge) after reflection/refraction.                                                                           • Surface: Formed by concave mirrors (when object is beyond focus) or convex lenses.                                                                                                                    • Properties:  o Can be projected on a screen. o Usually inverted compared to the object.                                       Example: Image on a cinema screen formed by a projector lens.                                                                                                                              2️⃣Virtual Image                                                                                                                                                                                                       • Formation: Light rays appear to meet when extended backward (they don’t actually converge).                                   • Surface: Formed by plane mirrors, convex mirrors, and concave lenses.                                                                                         • Properties:  Cannot be projected on a screen. o Always erect (upright).                                                                                                    Example: Your reflection in a bathroom mirror. 

 1️⃣Parallel Ray Rule                                                                                                                                                                                               • Concave Mirror: A ray parallel to the principal axis reflects through the focus (F).                                                                     • Convex Mirror: A ray parallel to the axis reflects outward, appearing to come from the focus (F) behind the mirror.                                                                                                                                                                                                                    2️⃣Focus Ray Rule                                                                                                                                                                                                      • Concave Mirror: A ray passing through the focus (F) reflects parallel to the principal axis.                                                      • Convex Mirror: A ray directed toward the focus (F) reflects parallel to the axis.                                                                       3️⃣ Centre of Curvature Rule                                                                                                                                                                                     • Both Mirrors: A ray passing through or directed toward the centre of curvature (C) reflects back along the same path.                                                                                                                                                                                                                  4️⃣ Oblique Ray Rule                                                                                                                                                                                                 • Both Mirrors: A ray hitting the pole (P) at an angle reflects at the same angle (law of reflection). 

 1.  Myopia (Nearsightedness):                                                                                                                                                                           • Imagine a camera that’s permanently zoomed in. It takes great close-up shots, but distant scenes are blurry. That’s like an eye with myopia — it focuses light in front of the retina, so far objects look fuzzy.                         2. Hypermetropia (Farsightedness):                                                                                                                                                               • Now picture a camera that’s stuck in wide-angle mode. It captures distant views clearly but struggles with close-ups. That’s hypermetropia — the eye focuses on light behind the retina, making nearby objects blurry.                                                                                                                                                              3. Presbyopia (Age-related Farsightedness):                                                                                                                                         Think of an old camera with a stiff lens that can’t adjust focus anymore. Whether the subject is near or far, it’s hard to get a sharp image. That’s presbyopia — the lens loses flexibility with age, affecting both near and far vision.                                                                                                                                                                                                                          • Myopia (Nearsightedness):-                                                                                                                                                                                     o Lens used: Concave lens (also called a diverging lens)                                                                                                                       o Reason: Eyeball is too long, or the cornea is too curved, causing light rays to focus in front of the retina.                      o Function: Spreads out light rays so they focus directly on the retina.                                                                                                                                              • Hypermetropia (Farsightedness) :-                                                                                                                                                                       o Lens used: Convex lens (also called a converging lens)                                                                                                                    o Reason: Eyeball is too short, or the cornea is too flat, causing light rays to focus behind the retina.                                                                 o Function: Bends light rays inward to help them focus on the retina.                                                                                                                                                 • Presbyopia (Age-related Farsightedness) :-                                                                                                                                                   o Lens used: Convex lens or Bifocal lens                                                                                                                                                        o Reason: Caused by loss of flexibility in the eye’s lens due to aging.                                                                                               o Function: Helps focus light from both near and far objects onto the retina, compensating for the stiff lens