NCERT

The presesnt day theory for structure of Atom is developed through many discoveries and hypothesises. In class 12 Physics, Atom chapter includes development of the sturucture of atom, and theories in the path of development of present theory. Students can check the ordered points below;

1. Thomson's Model of the Atom
2. Rutherford's Nuclear Model
3. Bohr's Model of the Hydrogen Atom
4. De Broglie's Hypothesis
5. Energy Emission Spectrum

These throries have been used to introduced the current theory of structure of atom.

Students who are preparing for the class 12 board exams needs additional practice questions after completing the NCERT Exercises. We have provided practice questions with accurate and atep-by-step solutions for students to better prepare for the board exams. Students can check the below provided link to access our additional practice questions along with previous year questions.

Chapter 12 Atoms NCERT Solutions 

Electromagnetic waves do not require a medium to propagate because they generate self-sustaining oscillations of magnetic and electric fields. Hence, it can travel through the vacuum of space. A changing magnetic field generates an electric field and vice versa. This property allows the wave to carry energy across space. The phenomenon is applicable to sunlight and other forms of EM radiation that travel through space to reach Earth. They cover millions of kilometers while reaching Earth. The EM wave theory is fundamental to understanding phenomena like cosmic observations, satellite communication, and solar radiation.

The entire range of electromagnetic radiation, arranged to increase and decrease the wavelength is called the electromagnetic (EM) spectrum. In the following order, it includes - radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. All these regions have unique properties and applications. For example, X-rays used in medical imaging,  visible light in everyday vision, infrared in remote controls and thermal imaging and radio waves are used in communication. This is an important concept that helps in classifying and utilizing different EM waves.

The photoelectric effect when light is projected in a metal surface, it's surface ejects electron (which are in outermost shell or free electron). This happens because the light provides additional energy to the electron to detach itself from metal surface. Well to do this light must have a certain amount of energy which in other words can be said the right frequency of light is required for photoelectric effect. 

This frequency must be above a certain minimum value (called threshold frequency) fixed for every metal, regardless of its intensity. Photoelectric effect cannot be explained by the wave theory of light.

The net magnetic flux through any closed surface is zero, according to Gauss's Law for magnetism.
Mathematically,
? B · dA = 0.
It states that all magnetic field lines that enter a surface must exit from it as well. In this way, it is different from the electric charges which can exist independently as positive and negative.

The Earth's magnetic field makes a magnetic inclination or dip with the horizontal plane at a particular location. It shows how much the magnetic field is tilted from the horizontal. It gets tilted due to the Earth's magnetic nature. The formula is:
tan I = B_V / B_H,
where B_V is the vertical component and B_H is the horizontal component of the Earth's magnetic field.

The angle between the magnetic north (the direction a compass points) and the geographic north (true north) is the magnetic declination. This angle can change over time due to changes in the Earth's magnetic field and varies with location on Earth. It is important for navigation where accurate directional orientation is crucial, especially in marine and aviation transport. The declination helps in avoiding navigational errors as it ensures that compass readings are corrected.