JEE Mains · Physics · STD 12 - 9. Ray optics and optical instruments
In a reflecting telescope, a secondary mirror is used to:
- A reduce the problem of mechanical support
- B remove spherical aberration
- C make chromatic aberration zero
- D move the eyepiece outside the telescopic tube
Answer & Solution
Correct Answer
(D) move the eyepiece outside the telescopic tube
Step-by-step Solution
Detailed explanation
It has advantage of a large focal length in a short telescope
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Physics
- An alternating voltage \(\mathrm{V}(\mathrm{t})=220 \sin 100 \ \pi \mathrm{t}\) volt is applied to a purely resistive load of \(50\ \Omega\). The time taken for the current to rise from half of the peak value to the peak value is _______.JEE Mains 2024 Hard
- Considering the Bohr model of hydrogen like atoms, the ratio of the ratio of the radius \(5^{\text {th}}\) orbit of the electron in \(\mathrm{Li}^{2+}\) and \(\mathrm{He}^{+}\) is _______.JEE Mains 2025 Easy
- A train blowing a whistle of frequency \(320\,Hz\) approaches an observer standing on the platform at a speed of \(66\,m / s\). The frequency observed by the observer will be (given speed of sound \(=330\,ms ^{-1}\) ) \(.............Hz\).JEE Mains 2023 Easy
- Two radioactive materials \(A\) and \(B\) have decay constants \(25 \lambda\) and \(16 \lambda\) respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of \(B\) to that of \(A\) will be "\(e\)" after a time \(\frac{1}{a \lambda}\). The value of \(a\) is \(......\)JEE Mains 2022 Medium
- The \(B-H\) curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solenoid with \(1000\, turns/cm\) . The current that should be passed in the solenoid to demagnetise the ferromagnet completely is
JEE Mains 2018 Medium - A rod with circular cross-section area \(2\,cm ^2\) and length \(40\,cm\) is wound uniformly with \(400\) turns of an insulated wire. If a current of \(0.4\,A\) flows in the wire windings, the total magnetic flux produced inside windings is \(4\,\pi \times 10^{-6}\,Wb\). The relative permeability of the rod is (Given : Permeability of vacuum \(\left.\mu_0=4 \pi \times 10^{-7} \;NA ^{-2}\right)\)JEE Mains 2023 Medium
More PYQs from JEE Mains
- The value of \(\left(2 .{ }^{1} P _{0}-3 .{ }^{2} P _{1}+4 .{ }^{3} P _{2}-\ldots .\right.\) up to \(51\) th term)+\(\left(1 !-2 !+3 !-\ldots . .\right.\) up to \(51^{\text {th }}\) term \()\) is equal toJEE Mains 2020 Medium
- A telescope with objective diameter \(R\) is used to observe a distant star emitting light of wavelength \(500\) nm, at a resolution of \(5 \times 10^{-7}\) radian. The value of \(R\) is _____ cm.JEE Mains 2026 Medium
- \(ABC\) is a plane lamina of the shape of an equilateral triagnle. \(D,\) \(E\) are mid points of \(AB\), \(AC\) and \(G\) is the centroid of the lamina. Moment of inertia of the lamina about an axis passing through \(G\) and perpendicular to the plane \(ABC\) is \(I _{0} .\) If part \(ADE\) is removed, the moment of inertia of the remaining part about the same axis is \(\frac{ NI _{0}}{16}\) where \(N\) is an integer. Value of \(N\) is
JEE Mains 2020 Hard - A particle is projected with velocity \(v_{0}\) along \(x-\) axis. A damping force is acting on the particle which is proportional to the square of the distance from the origin i.e., \(ma =-\alpha x ^{2}.\) The distance at which the particle stops:JEE Mains 2021 Hard
- The magnetic field in a region is given by \(\overrightarrow{ B }= B _{0}\left(\frac{ x }{ a }\right) \,\hat{ k }\). A square loop of side \(d\) is placed with its edges along the \(x\) and \(y\) axes. The loop is moved with a constant velocity \(\overrightarrow{ v }= v _{0} \hat{ i }\). The emf induced in the loop is:
JEE Mains 2021 Hard - Let \(\vec a = 3\hat i + 2\hat j + x\hat k\) and \(\vec b = \hat i - \hat j + \hat k\), for some real \(x\). Then \(\left| {\vec a \times \vec b} \right| = r\) is possible ifJEE Mains 2019 Hard