Practice Paper For NEET UG 2026 (Day 43)

Practice Paper For NEET UG 2026 (Day 43): Hello, my dear future Doctors! Day 43 is here, and you’re officially in the “serious contender” zone now! At this stage of your NEET UG 2026 journey, every practice paper isn’t just a test; it’s a power-up. Think of today’s paper as your personal learning experience, designed to sharpen your accuracy, boost your confidence, and help you spot those silly mistakes before the real exam does. So grab your pen, set that timer, and dive in with full energy because every question you solve today is one step closer to your dream medical college.

Q.1. In a Young’s double-slit experiment, the two slits are illuminated by a coherent monochromatic source of wavelength $\lambda$. If a thin transparent film of refractive index $\mu$ and thickness $t$ is introduced in front of one slit, the central maximum shifts by $n$ fringes. Which expression for $t$ is correct? ($d$ is slit separation, $D$ is distance to screen)

A. $t={\displaystyle \frac{n\lambda D}{(\mu -1)d}}$

B. $t={\displaystyle \frac{n\lambda d}{(\mu -1)D}}$

C. $t={\displaystyle \frac{n\lambda }{\mu }}$

D. $t={\displaystyle \frac{n\lambda }{(\mu -1)}}$

Q.2. A block of mass $m$ is placed on a rough horizontal surface with coefficient of friction $\mu$. A time-varying horizontal force $F(t)=kt$ (where $k$ is a constant) is applied. The block just starts to move at time $t_0$. What is $t_0$?

A. $t_0={\displaystyle \frac{\mu mg}{k}}$

B. $t_0=\mu mgk$

C. $t_0={\displaystyle \frac{mg}{\mu k}}$

D. $t_0={\displaystyle \frac{k}{\mu mg}}$

Q.3. A long solenoid of length $L$, cross-sectional area $A$, and $N$ turns carries a current I. A bar of soft iron of relative permeability ${\mu }_r$ completely fills the interior. What is the magnetic energy stored per unit volume inside the solenoid?

A. ${\displaystyle \frac{1}{2}}{\mu }_{0}n{I}^2$

B. ${\displaystyle \frac{1}{2}}{\mu }_0{\mu }_r{n}^2{I}^2$

C. ${\displaystyle \frac{1}{2}}{\mu }_0{n}^2{I}^2$

D. ${\displaystyle \frac{1}{2}}{\mu }_0{\mu }_r^2{n}^2{I}^2$

Q.4. In Ray optics, a real object is placed between the optical centre and focus of a convex lens. Which statement about the image formed is correct, assuming the lens is thin and in air?

A. The image is real, upright, and diminished on the opposite side of the lens

B. The image is virtual, inverted, and diminished on the same side as the object

C. The image is real, inverted, and enlarged on the opposite side of the lens

D. The image is virtual, upright, and enlarged on the same side as the object

Q.5. In electrostatics, a conducting spherical shell is given a charge $+Q$. A point charge $+q$ is then placed at the centre of the cavity inside the shell. What will be the net charge on the outer surface of the shell?

A. $+Q+q$

B. q

C. $+Q-q$

D. +Q

Q.6. In thermodynamics, which of the following is an intensive property and also a state function?

A. Molar enthalpy Hˉ

B. Internal energy $U$

C. Heat $q$

D. Work $w$

Q.7. Consider the following reaction mechanism:
${\text{NO}}_2+{\text{F}}_2\to {\text{NO}}_2\text{F}+\text{F}$ (slow)
$\text{F}+{\text{NO}}_2\to {\text{NO}}_2\text{F}$ (fast)
What is the rate law for the overall reaction $2{\text{NO}}_2+{\text{F}}_2\to 2{\text{NO}}_2\text{F}$?

A. Rate $=k[{\text{NO}}_2{]}^2$

B. Rate $=k[{\text{NO}}_2][{\text{F}}_2]$

C. Rate $=k[{\text{NO}}_2{]}^2[{\text{F}}_2]$

D. Rate $=k[{\text{NO}}_2][\text{F}]$

Q.8. In coordination chemistry, the complex $[{\text{Co(NH}}_3{\text{)}}_6]{\text{Cl}}_3$ is found to be diamagnetic. What does this imply about the electronic configuration and hybridization of cobalt in this complex? (Atomic number of Co = 27)

A. It is ${\text{Co}}^{2+}$ with $3d^7$ configuration and $s{p}^3{d}^2$ hybridization

B. It is ${\text{Co}}^{3+}$ with $3d^5$ configuration and $s{p}^3{d}^2$ hybridization

C. It is ${\text{Co}}^{2+}$ with $3d^7$ configuration and $d^{2}s{p}^3$ hybridization

D. It is ${\text{Co}}^{3+}$ with $3d^6$ configuration and $d^{2}s{p}^3$ hybridization

Q.9. For an organic compound, the molecular formula is ${\text{C}}_4{\text{H}}_8\text{O}$. On treatment with Tollens’ reagent, it gives a positive test and on reduction with ${\text{NaBH}}_4$ it forms a chiral alcohol. Which structure is most consistent with this information?

A. Butanone

B. Butanal

C. 2-Methylpropanal

D. Cyclobutanol

Q.10. The electronic configuration of an element X is $[\text{Ar}]3d^{5}4s^1$. Which statement about X and its common oxidation states is most appropriate?

A. X is chromium and the +3 oxidation state is generally more stable than +6 in aqueous solution

B. X is manganese and commonly shows +2 and +7 oxidation states only

C. X is iron and commonly shows +2 and +3 oxidation states only

D. X is chromium and the +6 oxidation state is more stable than +3 in aqueous solution

Q.11. In human physiology, which of the following best explains why the oxygen-hemoglobin dissociation curve shifts to the right during strenuous exercise?

A. Increased ${\text{CO}}_2$, increased temperature, and decreased $\text{pH}$ in active tissues

B. Decreased 2,3-BPG levels in red blood cells during exercise

C. Lower metabolic rate in muscles reducing oxygen demand

D. Decreased ${\text{CO}}_2$ production in muscles and decreased temperature

Q.12. The sliding filament theory of muscle contraction proposes that

A. Actin filaments actively shorten while myosin filaments remain constant in length

B. Both actin and myosin filaments shorten during contraction

C. Neither actin nor myosin filaments change length; they slide past each other

D. Myosin filaments actively shorten while actin filaments remain constant in length

Q.13. Which of the following is the most likely immediate effect of a sudden increase in blood pressure detected by baroreceptors in the carotid sinus?

A. Increased vagal (parasympathetic) output leading to bradycardia

B. Increased sympathetic outflow leading to vasoconstriction and increased heart rate

C. Stimulation of renin release from the kidneys to raise blood pressure

D. Decreased parasympathetic activity causing tachycardia

Q.14. During spermatogenesis in humans, which cell type is the first to become haploid?

A. Primary spermatocyte

B. Spermatogonium

C. Spermatid

D. Secondary spermatocyte

Q.15. Which of the following ecological concepts refers specifically to the range of environmental conditions under which a species can maintain a stable population in the presence of competitors?

A. Realized niche

B. Ecotone

C. Fundamental niche

D. Keystone species

As you wrap up Day 43, remember that progress isn’t just about marks, it’s about learning, improving, and showing up consistently. Every mistake you analyze today is a lesson secured for tomorrow. Stay calm, stay focused, and trust the process you’ve been building all along. You’re closer than you think, and with this kind of dedication, success in NEET UG 2026 is not just a goal, it’s an outcome waiting for you. Keep going, future doctor!

I sincerely apologize for making you all wait for the daily practice questions. I wasn’t keeping well physically, which made it difficult for me to sit and prepare new sets for you, and I truly regret the delay.

Now, with the exams approaching, I’m fully back and committed to supporting you there will be daily practice sets along with NEET-related updates, even on Sundays. So stay tuned, keep studying, and let’s stay consistent together!

ANSWERS & EXPLANATIONS

Ans.1. B. T$t={\displaystyle \frac{n\lambda d}{(\mu -1)D}}$. Here, $(\mu -1)t$, quantifies how much extra optical length the light travels in the film compared to air. This additional optical path corresponds to a certain number of fringe shifts, which are determined by the wavelength and the geometry of the experimental setup. Hence, any expression not involving $(\mu -1)$ and the ratio $d\mathrm{/}D$ cannot correctly predict the observed shift in the central maximum.

Ans.2. A. $t_0={\displaystyle \frac{\mu mg}{k}}$. The block starts moving when the applied force equals the maximum static friction, so $k{t}_0=\mu mg$. Solving this equation directly gives $t_0={\displaystyle \frac{\mu mg}{k}}$. This respects the physical interpretation that friction grows with $\mu$, delaying the onset of motion.

Ans .3. B.  is: ${\displaystyle \frac{1}{2}}{\mu }_0{\mu }_r{n}^2{I}^2$. The magnetic field inside a long solenoid filled with a linear magnetic medium is $B={\mu }_0{\mu }_{r}nI$, where $n={\displaystyle \frac{N}{L}}$ is the turn density. The energy density in a magnetic field is $u={\displaystyle \frac{B^2}{2\mu }}$. Substituting $B$ and $\mu ={\mu }_0{\mu }_r$, we obtain $u={\displaystyle \frac{1}{2}}{\mu }_0{\mu }_r{n}^2{I}^2$.

Ans. 4. D. The image is virtual, upright, and enlarged on the same side as the object. This matches the typical use of a convex lens as a magnifier, where the image appears larger, upright, and located on the same side of the lens as the object when viewed by the observer.

Ans. 5. A. +Q+q. This combination of $-q$ on the inner surface and $+Q+q$ on the outer surface conserves the total shell charge at $+Q$.

Ans.6. A. Molar enthalpy Hˉ. This quantity encapsulates the energy content per mole in a way that is independent of the total amount of substance, and like enthalpy, it is a state function depending only on the system’s thermodynamic state.

Ans.7. B. Rate $=k[{\text{NO}}_2][{\text{F}}_2]$. This reflects the bimolecular nature of the rate-determining step, which decides the actual kinetic orders.

Ans. 8. D. It is ${\text{Co}}^{3+}$ with $3d^6$ configuration and $d^{2}s{p}^3$ hybridization. In the presence of strong-field ligands like ammonia, ${\text{Co}}^{3+}$ can form a low-spin octahedral complex where the $3d$ electrons pair up, leading to $d^{2}s{p}^3$ inner orbital hybridization and diamagnetism.

Ans .9. C. 2-Methylpropanal. When 2-methylpropanal is reduced, it forms 2-methylpropan-1-ol, where the alcohol-bearing carbon is attached to a hydroxyl group, a hydrogen, a methyl group, and an isopropyl group, all different, making it a chiral centre. This fits both the positive Tollens’ test and the formation of a chiral alcohol.

Ans .10. A. X is chromium and the +3 oxidation state is generally more stable than +6 in aqueous solution. Chromium’s actual configuration is the one given, and its aqueous chemistry is dominated by ${\text{Cr}}^{3+}$ due to the thermodynamic and kinetic stability of this state compared with ${\text{Cr}}^{6+}$, which tends to act as a strong oxidizing agent and is more stable in alkaline rather than neutral aqueous conditions.

Ans .11. A. Increased ${\text{CO}}_2$, increased temperature, and decreased $\text{pH}$ in active tissues. While 2,3-BPG is indeed an important modulator of hemoglobin affinity for oxygen and higher levels promote a rightward shift, the immediate rightward shift during acute exercise is primarily driven by increased ${\text{CO}}_2$, heat, and acidity in the working muscles. Together, these changes modify hemoglobin’s conformation to favour oxygen unloading, ensuring that active tissues receive adequate oxygen to meet their heightened energy demands.

Ans .12. C. Neither actin nor myosin filaments change length; they slide past each other. According to the sliding filament theory, muscle contraction results from the relative sliding of actin (thin) filaments over myosin (thick) filaments. Cross-bridge cycling, powered by ATP hydrolysis, allows myosin heads to attach to actin, pivot, and pull the thin filaments toward the centre of the sarcomere. This shortens the sarcomere and thus the muscle fibre, but the actual length of each filament stays the same. Changes in band patterns seen under the microscope (such as narrowing of the I-band and H-zone) are due to overlap changes, not filament shortening.

Ans.13. A. Increased vagal (parasympathetic) output leading to bradycardia. The baroreceptors are key components of short-term blood pressure regulation. When arterial pressure acutely rises, these receptors stretch and increase their firing rate along the glossopharyngeal and vagus nerves to the medulla oblongata. The medullary cardiovascular centre responds by inhibiting sympathetic pathways and stimulating parasympathetic (vagal) fibres to the heart. Increased vagal activity slows the sinoatrial node, reducing heart rate, and thereby decreases cardiac output and arterial pressure. This rapid reflex helps stabilize blood pressure on a beat-to-beat basis.

Ans. 14. D. Secondary spermatocyte. In the testis, spermatogonia (2n) located near the basement membrane proliferate by mitosis. Some of these differentiate into primary spermatocytes, which still possess a diploid chromosome number but with replicated DNA. During meiosis I, homologous chromosomes pair and segregate, reducing the chromosome number from diploid to haploid. The products of meiosis I are the secondary spermatocytes, which are therefore haploid (n), each containing one member of each homologous pair, though each chromosome is still duplicated. Subsequent meiosis II separates sister chromatids, producing spermatids, but the key point is that the secondary spermatocyte represents the first haploid stage of spermatogenesis.

Ans .15. A. Realized niche. The concept focuses on the interaction between a species’ potential environmental tolerances and the limiting effect of competition and other biotic factors. The realized niche is thus smaller than or equal to the fundamental niche and captures where a species can maintain stable populations under real-world community interactions, unlike the broader, theoretical envelope of the fundamental niche.