Oral Recitation Science

• Importance of tectonic boundaries on our earth's surface.

  geological activity, habitability, understanding the earth's processes
• How does subduction happen?

  • Subduction occurs at convergent boundaries when one tectonic plate moves beneath another
  • Typically involves denser oceanic plates sliding beneath less dense continental plates
  • Leads to forming trenches, volcanic arcs, and mountain ranges.
• process of convergent plate boundary


  At a convergent plate boundary, two tectonic plates collide. One plate is forced beneath the other in a process called subduction. This collision can lead to earthquakes, volcanic activity, and the formation of mountain ranges.
• process of divergent plate boundary

  Two tectonic plates move apart from each other. These boundaries are formed by convection in the Earth's mantle, facilitating the rise of material, heat, and a reduction in pressure that melts rock beneath the rift areas, causing flood basalt or lava flows.
• Process of Transform Plate Boundary

  • Plates slide past each other horizontally
  • No crust created or destroyed
  • Causes earthquakes and rock displacement
  • Creates ridges and valleys along a strike-slip fault
  • Common in oceanic divergent boundaries
  • Example: San Andreas Fault in California
• according to Wegener, how does a continental jigsaw puzzle serve as evidence for one supercontinent?

  • Wegener observed continents fit together like a jigsaw puzzle
  • Similar rocks and fossils found on opposite coastlines
• How Coal Deposits Support Wegener's Supercontinent Theory

  • Wegener noted that ancient coal seams and coral reef fossils are found in locations that are now much too cold to support their growth
  • This suggests these organisms lived in warmer climate zones and their fossils/deposits later drifted to new locations as the continents moved
  • This evidence supports Wegener's theory that the continents were once connected as a single supercontinent
• Fossils as Evidence for Pangaea

  • Fossils of the same plant and animal species found on separate, now-distant continents:
  • These shared fossils indicate the continents were once connected as the supercontinent Pangaea, before drifting apart over millions of years.
  • The presence of these fossils across widely separated modern continents supports Wegener's theory of continental drift.
• Convection currents


  convection currents are created by differences in temperature and density within a fluid, causing the warmer, less dense fluid to rise and the cooler, denser fluid to sink, resulting in a circular flow pattern. 
• Why do tectonic plates exist?

  • Earth's layered structure allows the crust to break into distinct, moving plates
  • Convection in the mantle, driven by internal heat, drives plate movement
  • Cracking of the brittle lithosphere forms plate boundaries
  • Plate interactions at boundaries create geological features
  • Plate size and composition influence plate movement and interactions
• relationship of frequency and wavelength

  • Wavelength (λ) and frequency (ν) are inversely related in the electromagnetic spectrum
  • As the wavelength decreases, frequency increases, and vice versa
  • Lower frequency waves (e.g., radio waves) have longer wavelengths and lower energy
  • Higher frequency waves (e.g., X-rays, gamma rays) have shorter wavelengths and higher energy
• Importance of Radio waves


  Radio waves are a crucial component of our daily lives, enabling various forms of wireless communication and technology. They are the foundation of many essential systems and services we rely on.
• Importance of Infrared

  • Remote Controls: Infrared enables remote control of devices.
  • Thermal Imaging: Helps in night vision and surveillance.
  • Astronomy: Observing cooler objects in the universe.
  • Communication: Used in fiber optic cables for data transmission.
  • Health: Used in thermal therapy for pain relief.
  • Environmental Monitoring: Helps study Earth's thermal emission for climate monitoring.
• Importance of Microwave

  • Microwaves heat food efficiently in microwave ovens
  • Crucial for communication technology like satellite TV
  • Used in radio tagging technology (RFID) for quick item scanning
  • Integral in radar systems for determining distances to objects
• Importance of Visible Light

  • Vision: Visible light enables us to see and perceive our surroundings.
  • Applications: Visible light is used in medical, cosmetic, and scientific applications.
  • Energy and Lighting: Visible light from the sun and artificial sources provides energy and illumination for our daily activities.
• Importance of uv rays

  • Vitamin D production: UV-B light from the sun triggers the body's production of essential vitamin D.
  • Disinfection and sterilization: UV light is used to kill microorganisms, making it useful for disinfection and sterilization.
  • Fluorescence and detection: UV light causes certain materials to fluoresce, enabling applications in art, security, and forensics.
  • Medical and scientific uses: UV light is used in research, treatments, and manufacturing processes.
  • Skin and eye damage: Excessive UV exposure can cause sunburn, skin aging, cancer, and eye conditions like cataracts.
• Importance of X-ray

  • Medical Diagnosis and Treatment:
  • X-rays are widely used to detect broken bones, tumors, and other internal issues, allowing for early diagnosis and effective treatment.
  • X-rays are used in radiation therapy to target and kill cancer cells.
  • Mammograms, a type of X-ray, help detect breast cancer early, improving treatment success rates.
  • Security Screening:
  • X-ray scanners are used at airports, train stations, and other security checkpoints to detect contraband items such as weapons and drugs.
• Importance of Gamma Ray


  • Medical imaging and cancer treatment • Sterilization and pasteurization

  • Industrial applications and security • Space exploration and astronomy • Quality control and origin determination
• Benefits of Exposing Skin to Mild Morning Sunlight

  • Activates precursors of Vitamin D in the skin
  • Vitamin D is essential for:
  • Improving bone health
  • Strengthening the immune system
  • Preventing cancer
  • Reducing fat
  • Healing minor hormonal problems
  • Regulates the body's circadian rhythm, aiding in better sleep patterns.
  • Helps in the production of melatonin, which influences sleep patterns and energy levels
• Why is it not advised to undergo an x-ray several times?

  • Repeated X-ray exposure increases the cumulative risk of adverse effects from radiation
  • Higher doses lead to risks like skin problems, infertility, cataracts, and hair loss
• Suppose an object is placed in front of a plane mirror, what would be the image location, orientation, size, and type?

  Image Location

  • The image is located behind the mirror, at the same distance from the mirror as the object.

  Image Orientation

  • The image is upright, but left-right reversed compared to the object.

  Image Size

  • The image is the same size as the object. The magnification is 1.

  Image Type

  • The image formed is a virtual image, meaning the light rays do not actually pass through the image location. The image appears to be behind the mirror, but cannot be projected onto a screen.
• When does an image become of same size with the object in a concave mirror?


  An image becomes of the same size as the object in a concave mirror when the object is placed at the centre of curvature of the mirror
• No Image in Concave Mirror

  1. When the object is at the focal point (F) of a concave mirror

  2. Light rays from the object pass through the focal point without meeting

  3. Resulting in no image
• Image formation in concave mirrors


  • Object between F and the mirror forms a virtual, upright, magnified image
  • Object beyond C forms a real, inverted, diminished image
• When does an image become virtual in a concave mirror?

  • Real image: Object beyond one focal length
  • Virtual image: Object in front of the focal point 2345
• Concave mirrors


  • Reflective inner surface
  • Real focal point in front of the mirror
  • Can form real and virtual images
  • Can form magnified, diminished, or same-sized images depending on object position
  • Can form upright and inverted images
• Convex mirrors


  • Reflective outer surface
  • Virtual focal point behind the mirror
  • Only form virtual images
  • Always form diminished images
  • Always form upright images
  • Provide a wider field of view
• When does an image become of same size with the object in a convex lens?

  An image of the same size as the object is obtained when the object is placed at a distance equal to 2F from a convex lens, where F is the focal length of the lens.
• When does it happen that no image is seen in a convex lens?

  • When the object is placed at the focal point (F) of the convex lens
  • In this case, the light rays from the object exit the lens parallel to each other after refraction
  • Since the light rays do not converge to form a real image, no image can be seen by looking through the lens or projecting it onto a screen
  • This is because the object is located at the focal length (F) of the convex lens, so the light rays remain parallel after passing through the lens
• When does an image become virtual in a convex lens?

  • When the object is beyond the focal point, the lens forms a real, inverted image
  • When the object is between the lens and focal point, the lens forms a virtual, upright image
  • The virtual image is formed because the light rays diverge after passing through the lens, rather than converging
  • The virtual image appears to be coming from behind the lens, even though no actual image is formed there
  • The virtual image is always upright and can be magnified compared to the object
• Image Projection of Convex Lenses

  • Converges light rays to form real, inverted images
  • Can create virtual images under certain conditions
  • Images can be smaller, same size, or larger than the object
  • Used in cameras, telescopes, microscopes, and corrective eyeglasses
• Image projection of Concave lenses

  • Diverges light rays to form virtual, upright, and smaller images
  • Image is always virtual and diminished
  • Forms a real, highly diminished image at the focus when the object is at infinity
  • Used in telescopes, spy holes, and for correcting nearsightedness
• What is the importance of plane mirrors to our daily lives?

  • Plane mirrors are essential for cosmetic purposes, providing reflections for grooming and dressing.
  • They are used in vehicles as rearview mirrors for safety and better visibility.
  • In scientific instruments like microscopes and telescopes, plane mirrors ensure high-quality image reflection.
  • Everyday applications such as torchlights and projectors utilize plane mirrors for even light distribution.
  • Plane mirrors help create the illusion of larger and brighter spaces due to their reflective properties.
• What is the importance of concave mirrors to our daily lives?

  • Makeup mirrors: Providing magnified, detailed views for makeup application.
  • Dental examinations: Assisting dentists in examining and treating oral health issues.
  • Shaving mirrors: Offering magnified, clear reflections for precise grooming.
  • Telescopes and microscopes: Enabling the observation of distant or small objects by gathering and focusing light effectively.
• What is the importance of convex mirror to our daily lives?

  • Enhances road safety by reducing blind spots for drivers
  • Helps people see around corners in buildings to prevent collisions
  • Used for security near ATMs to check for individuals behind users
  • Functions as magnifying glasses and in telescopes for creating smaller virtual images of objects
• What is the importance of a convex lens to our daily lives?

  • Correcting hypermetropia (far-sightedness) in eyeglasses
  • Magnification and focusing in optical instruments like microscopes, binoculars, and telescopes
  • Focusing and magnifying images in cameras
  • Enlarging objects with magnifying glasses
• What is the importance of concave lens to our daily lives?

  • Corrects nearsightedness (myopia) by spreading out light before it reaches the eye
  • Used in flashlights to widen the beam of light
  • Utilized in peepholes to provide a wider view of the surroundings
  • Employed in optical devices like binoculars and telescopes to ensure correct color representation
  • Used in photography to correct color errors and widen the field of view, creating a fisheye effect

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• How is the current induced between a bar magnet and a coil?

  • Moving a bar magnet near a coil generates a changing magnetic field.
  • This change induces an electric current in the coil.
  • The direction of the induced current is determined by the movement of the magnet.
  • Lenz's Law states that the induced current opposes the change in the magnetic field.
  • Therefore, the direction of the induced current depends on how the magnet is moved relative to the coil.

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• • Generator:
  • Converts mechanical energy into electrical energy
  • Mechanical force (e.g. from a turbine) drives the generator shaft
  • This induces an electromotive force (EMF) in the armature windings, generating an electric current
  • Electric Motor:
  • Converts electrical energy into mechanical energy
  • Electricity is supplied to the armature windings
  • This creates a magnetic force that drives the motor shaft, producing mechanical motion
• What is puberty and how does it happen?

  Puberty is the process of physical and hormonal changes that occur during the transition from childhood to adulthood. It is triggered by the release of hormones that cause the body to develop and mature sexually