Electromagnetic Spectrum


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The electromagnetic spectrum is the range of all types of electromagnetic radiation. Electromagnetic radiation consists of waves of electric and magnetic fields that propagate through space at the speed of light. The different types of electromagnetic radiation are differentiated by their frequency or wavelength.

The electromagnetic spectrum includes several types of radiation, including:

  1. Radio Waves: These have the longest wavelength and the lowest frequency in the electromagnetic spectrum. They are used for radio and television broadcasting, as well as communication and navigation systems.
  2. Microwaves: These have a higher frequency and shorter wavelength than radio waves. They are used for communication, such as mobile phones and microwave ovens.
  3. Infrared Radiation: These have a higher frequency and shorter wavelength than microwaves. They are often used in thermal imaging cameras and remote controls.
  4. Visible Light: This is the only part of the electromagnetic spectrum that can be seen by the human eye. It consists of different colors with different wavelengths, ranging from violet to red.
  5. Ultraviolet Radiation: These have a higher frequency and shorter wavelength than visible light. They are responsible for sunburns and are also used in black lights and sterilization.
  6. X-rays: These have even higher frequency and shorter wavelength than UV radiation. They are used in medical imaging, such as CT scans and radiography.
  7. Gamma Rays: These have the highest frequency and the shortest wavelength in the electromagnetic spectrum. They are produced by nuclear reactions and are used in cancer treatment and nuclear medicine.

Each type of electromagnetic radiation has different properties and uses, but they all share the same fundamental characteristics of waves of electric and magnetic fields that propagate through space at the speed of light.

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Electric field point charges and direction of electric field.


An electric field is a physical quantity that describes the influence that electric charges have on each other. An electric field is a vector field, meaning that it has both a magnitude and a direction at each point in space.

Point charges are electric charges that are concentrated at a single point in space. The electric field created by a point charge at a point in space is given by Coulomb’s law:

E = k*q/r^2

where E is the electric field at the point, k is Coulomb’s constant, q is the charge of the point charge, and r is the distance between the point charge and the point where the electric field is being measured.

The direction of the electric field at a point in space is the direction in which a small positive test charge would be pushed or pulled if it were placed at that point. For a positive point charge, the electric field points radially outward from the charge, while for a negative point charge, the electric field points radially inward towards the charge.

The magnitude of the electric field decreases as the distance from the point charge increases. Therefore, the electric field created by a point charge becomes weaker as the distance from the charge increases. For more information see the video attached

A chemical bond


A chemical bond is a force that holds atoms together in a molecule. It is formed by the attraction between the positively charged nuclei of atoms and the negatively charged electrons surrounding them. The strength of this attraction is determined by the distance between the atoms and the number of electrons involved in the bond.

There are several types of chemical bonds, each with its own characteristics and properties. The most common types of chemical bonds are covalent, ionic, and metallic bonds.

Covalent bond: It is formed when two atoms share electrons. The shared electrons occupy a region of space called a molecular orbital, which is located between the nuclei of the two atoms. The strength of a covalent bond is determined by the number of electrons shared and the distance between the atoms. Covalent bonds are typically found in molecules made up of non-metal elements.

Ionic bond: It is formed when one atom donates an electron to another atom. The atom that loses an electron becomes positively charged and is called a cation, while the atom that gains an electron becomes negatively charged and is called an anion. The strength of an ionic bond is determined by the attraction between the positively and negatively charged ions. Ionic bonds are typically found in compounds made up of metal and non-metal elements.

Metallic bond: It is formed by the attraction between positively charged metal ions and a sea of delocalized electrons. The strength of a metallic bond is determined by the number of delocalized electrons and the distance between the metal ions. Metallic bonds are typically found in compounds made up of metal elements.

The net electrostatic force two atoms sharing electrons exert on each other is the chemical bond that holds atoms together in a molecule. Understanding the properties of chemical bonds is essential for understanding the behavior of molecules and their interactions with other molecules.

Grade 11 Newton Laws QUESTION


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A tow truck is towing a car using an inelastic steel cable (of negligible mass) as shown in the diagram below. The steel cable forms an angle of 30° with the horizontal.

The two vehicles move from rest on a straight, horizontal road to the right. The mass of the car is 1100 kg and the mass of the tow truck is 4000 kg. The tow truck’s engine applies a force of 15 000 N. A constant frictional force of 1456 N is acting on the car and a constant frictional force of 4520 N is acting on the tow truck respectively.

3.1 State Newton’s Second Law of motion, in words. (2)

3.2 Draw a labeled, free-body diagram of all the forces acting on the car. (4)

3.3 Calculate the:

3.3.1 acceleration of the car. (6)

3.3.2 magnitude of the tension T in the cable. (3)

3.5 Using equations of motion, calculate the distance that the car will travel in 4s. (2)

3.6 State Newton’s First Law of motion, in words. (2)

3.7 Use Newton’s laws of motion to explain why towing can be dangerous. (2)

3.8 If the force of horizontal tension in the cable, from the car on the truck, is 1890 N, what is the horizontal force of the truck on the car? Explain with reference to the relevant scientific principles. (2) [23]

 PHYSICAL SCIENCES GRADE 11 CONTROLLED TEST TERM 4 2021


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Paper shared with the help KC Kakinda