What is echo?

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Jasmine Grover

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In acoustics, an echo is a reflection of sound waves off a surface back to the listener after a delay of a few seconds or more.

  • Echo is the reflection of sound reaching the listener after some time.
  • It often creates a repetitive, distorted, and sometimes amplified effect.
  • It can occur naturally in environments with hard surfaces or be deliberately created for artistic or communication purposes using specialized equipment.

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CBSE CLASS XII Related Questions

  • 1.

    A circular coil of 100 turns and radius $\left(\frac{10}{\sqrt{\pi}}\right)$ cm carrying current of $5.0\,\text{A}$ is suspended vertically in a uniform horizontal magnetic field of $2.0\,\text{T}$. The field makes an angle $30^\circ$ with the normal to the coil. Calculate:

    (I) the magnetic dipole moment of the coil, and

    (II) the magnitude of the counter torque that must be applied to prevent the coil from turning.


      • 2.

        A ray of light MN is incident normally on the face corresponding with side AB of a prism with an isosceles right-angled triangular base ABC. Trace the path of the ray as it passes through the prism when the refractive index of the prism material is (i) $\sqrt{2}$, and (ii) $\sqrt{3}$.


          • 3.

            (I) The real image of an object placed between $f$ and $2f$ from a convex lens can be seen on a screen placed at the image location. If the screen is removed, is the image still there? Explain.

            (II) Plane and convex mirrors produce virtual images of objects. Can they produce real images under some circumstances? Explain.


              • 4.

                A rectangular loop of size 5 cm $\times$ 8 cm is lying in the $x$-$y$ plane in a uniform magnetic field $\vec{B} = (2.0\ \text{T})\hat{k}$. The total magnetic flux linked with the loop is:

                  • 80 Wb
                  • 16 Wb
                  • \(8 \times 10^{-2}\) Wb
                  • \(8 \times 10^{-3}\) Wb

                • 5.
                  The resistance of a metal wire at \(20^\circ\text{C}\) is \(1.05\,\Omega\) and at \(100^\circ\text{C}\) is \(1.38\,\Omega\). Determine the temperature coefficient of resistivity of this metal.


                    • 6.

                      Find the ratio $\dfrac{\lambda_\alpha}{\lambda_p}$ of the de Broglie wavelength $\lambda_\alpha$ associated with an alpha particle to the de Broglie wavelength $\lambda_p$ associated with a proton if both are moving with the same velocity.

                        CBSE CLASS XII Previous Year Papers

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